Changelog for Update 1.5.1 (added 23 March 2017):

Single-Player Gameplay
- Actors scheduled to trigger when a level ends will be immediately triggered,
- No more crash or multiple teleports when entering Adon's checkpoints,
- A clipping error was repaired in River of Souls,
- The Tek Bow can now snipe with normal arrows after loading a saved game,
- Improved player clipping near bridges,
- Sunfire Pods can now set fire to and kill Blind Ones,
- Improved behavior when unlocking levels, may fix game-breaking glitch with missing keys,
- The Primagen can no longer become stuck in mid-air between phases 2 and 3 of his battle,
- An infrequent crash during the Primagen boss fight has been fixed,
- Player skin sounds no longer carry over from multiplayer games,
- Quicksave slot can now be loaded from the Load Game menu, including from the titlescreen,
- Blind One and Queen boss warp cheats are no longer reversed,
- It is no longer possible to save the game when dead or when at the game over screen,
- Shredder is now treated with higher selection priority than the shotgun,
- A crash when re-entering a specific area of Lair of the Blind Ones has been fixed,
- Queen Boss mite spawning rate has been limited,
- Improved AI leashing behavior - enemies will not return to their idle locations if they can currently see the player or their target,
- Hidden enemy appearance particle effect will occur less often with partially hidden enemies,
- It should no longer be possible to become stuck in the Death Marshes due to missing ammo bunker door locks,
- Changing weapons is no longer possible while riding the Styracosaur,
- Death animation now fully stops instead of looping. This addresses a bad looping behavior in one of the flesh eater models.

Local Multiplayer
- Stability improvements,
- Local player setup will always be fully completed for splitscreen,
- Player radius is properly restored when becoming or ceasing to be the Monkey in Frag Tag,
- The nuke weapon will appear more rarely in Rok Mix mode,
- Local players in splitscreen can now independently change their ammo types,
- A point where the player could get stuck in the Port of Adia MP map has been repaired.

Audio
- Volume of ambient lava sounds reduced,
- Adon now announces the finding of Primagen keys,
- Tek arrow wind-up sound is no longer global, and is more consistent,
- Unique Raptoid sound effects from the N64 version have been imported,
- Turok now has unique pain sounds when taking damage from low oxygen while swimming,
- Shredder and shotgun firing sound effects improved,
- High-pitched noise eliminated from sound samples.

Renderer / Graphics
- Shader language version 4.00 is now properly accepted,
- Bloom: Opacity and intensity can now be set by the user,
- Optimizations for masked texture rendering and deferred shadow maps,
- AMD-specific fix for flashlight, deferred decals, and SAO,
- Pipeline synchronization is now an end-user option and is no longer enabled by default,
- Actor outlining effects now cooperate properly with resolution scaling.

User Interface
- Video resolution setting will be saved without having to exit the game,
- Font size increased on Bindings menu,
- Clearer distinction between Exit to Title and Quit in English and French languages,
- Support for AMD GPU memory queries on the graphics option menu,
- Technical graphics options menu added,
- Users with ISO European keyboards can now access the console, and can bind two additional language-specific keys on the keyboard to actions,
- Options added to control all forms of player head bobbing and tilting,
- Step values have been tweaked for all slider-type options,
- Mouse smoothing is now available from the menus, and no longer crashes the game if set to zero.

Misc
- "Operation completed successfully" is no longer reported as an error if GL context creation fails,
- Lag reduced when messages are added to the console,
- Crash in math routine repaired.
- For advanced users, new cvars have been added:
- jobs_concurrentThreads - Sets the number of concurrent threads to use. If set to 0 then no multithreading will be used
- jobs_prioritize - Setting to 0 marks all threaded jobs as low priority
- jobs_useTasks - Enables/disables job tasks
- "What's New" menu has been added to display Changelog information.
- The Queen and Mother bosses have received a health buff and now receive -50% explosion damage

Changelog for update 1.5.2 / (Windows) (added 11 April 2017):

Single-Player Gameplay

- Show both ammo types in the HUD for weapons with alternate ammo types
- Bug fixes for particle splash damage (non-explosive) setting off event link triggers
- All generators that should spawn random ammo now work
- Minor collision fixes in first Death Marsh level
- Fixed situation where player could become trapped in the spider-health trap chamber in River of Souls
- Fixed a crash when switching levels while enemies are being triggered by an event
- Charge dart now consumes 2 to 3 ammo based on charge level
- Wasp enemies are now more aggressive and will become responsive after being spawned
- Added fog effects to graveyard levels
- Tweaked razor wind to be more effective against enemies with metallic parts
- Trap doors in the crystal rooms in Lair of the Bline Ones now closes instantly, preventing sequence breaks
- Turrets will now cease firing if the target is obstructed

Renderer / Graphics

- Major performance gain in the main world deferred shader
- Addressed the 'checkerboard pattern' rendering glitch by avoiding depth buffer blitting,
- Non-deferred blood decals now adopt the proper red or green coloration depending on their source,

Local and Network Multiplayer

- Improved situations where protocol commands would become over-throttled when sending to latent nodes.
- Multithreaded packet transmission (which is on by default)
- New multiplayer chat message system
- Fixed issue with connecting to lobbies from startup
- Rebalanced damage curve of charge-dart against players
- Added mod and version filters to the multiplayer server lists
- Added support for changing the network transmission speed of the client/server (lower speeds reduces bandwidth requirements)
- Added support for custom map rotations
- Fixed an issue where team-games wouldn't clear their scores properly on map change
- Improved the reliability of sending information such as the scoreboard when a player connects to a game
- Numerous weapon balance and tweaks
- Three N64 multiplayer maps added (Bullseye, Crazy Eight, Experimentata)

Audio

- Voice volume setting is now independent of sound effect volume
- Support added for German localized voices

User Interface

- Ability to delete save games

Misc

- Fixed collision detection issue when shooting at an object that is up against a wall
- Better detection for avoiding pickups behind walls and other obstructions

No GOGchievements?

You have to ask GOG or the devs/pubs; I just posted the changelog.

Changelog for Update 1.5.5 (added 28 June 2017):

Renderer / Graphics
- Instanced rendering for particles (Direct X optimization)
- Shadow map optimizations (batched actor shadow casters)
- Uniform buffer optimizations (Direct X)
- Fixed cloaking effect not rendering
- Fixed explosions changing color when making contact with 'alien flesh' surface types
- Particles and trails can now be occluded by geometry (optimizations)

Single-Player Gameplay
- Destructibles now flash red when shot
- Fix turrets in River of Souls not firing at player
- Some components of the AI is now multi-threaded (optimizations)

Local and Network Multiplayer
- Dedicated server support (self hosted with included binary, server list browser built in)
- New InstaRok ("Instagib") game mode
- New Raptor-Fest (survival co-op/competitive) game mode
- Improved handling of large amounts of object synchronization
- Restored 3 N64 maps; Escheria, Endangered species and Moonlit Mayhem
- Stability updates
- Added 'playername' cvar to act as the local player name incase no social service (Steam/GOG Galaxy) is avalible

User Interface
- New quick weapon select feature

Misc
- Optimized collision detection with static meshes
- Fixed floating blood splats from shotgun bullets

Update 1.5.9 (05 October 2018)

Installation of the latest patch keeps failing.

There is no latest patch. Only a full 1.5.9 installer and that one does work 100% fine.

Looks like another update? 1.5.9.1

No changelog that i can see. Maybe a hotfix for some of the issues some people seem to be posting about?

Why is the GOG version of Turok 2 still missing the Mac & Linux versions from Steam? And missing achievements too.

I can't get the latest update at all, keeps saying server error.

Well just as always here on GOG: People asking for a native version on GNU/Linux and guess what ... they are ignored all the time by GOG. No communication, no further information, exactly nothing. And the version on Steam? Well, DRM, enough said about it because it doesn't run without the client. After a half year no further step forward, GOG. Really poor performance for a game here already released and having already a native version!

Two months later and still nothing to be seen about missing native ports for GNU/Linux and Mac. Well, that's odd and typical for GOG. But hey, some more shiny games released until then. Please, GOG-team: Care a little bit more about the games already released and available here. Some more information about missing content. That's all to be asked for!

And just more than two months: Any changes? Well, not for GNU/Linux and Mac at all. So business as usual: Windows is preferred, rest is treated second class.