Tip: Avoid Galaxy.

It's usually not mandatory, and given its UX leaves to be desired, if you MUST use a launcher, Heroic and Playnite could be good options.

If you can live without launchers, you can get installers through your library at https://www.gog.com/account.

Ya'lls?

I'm pretty sure, that's what he meant :)

If ya'lls don't make a proper distinction between 2nd person singular and 2nd person plural, ya'lls'll have to make one up eventually. Immortality to those of ya'lls that seize the moment. ;)

Try the following:
1) Close Galaxy (fully via System Tray)
2) Go to: %PROGRAMDATA%\GOG.com
3) Delete everything within
4) Go to: %LOCALAPPDATA%\GOG.com
5) Delete everything within
6) Launch Galaxy and try again.

If that does not work, please provide a screenshot of your login error.

I think it is short for "Your balls".

I must be odd, but I don't see much of difference using GOG Galaxy, Steam, Epic Games Launcher, Ubisoft Connect or the EA client (whatever it is called nowadays, the client icon is just called "EA").

They all do basically the same thing, let me buy games from the store, download and install them, run the games, uninstall the games, and they apparently have the same basic functionalities like cloud saves, auto-updates etc.

I really don't see much of difference in using each of them, so I really have to wonder how people are able to tell "this client is awful while that client is great"? How are they so different to use that you can make such a distinction?

It is a bit like whether I am using Firefox, Opera, Chrome or Edge browser; sure there are some slight differences and I might slightly favor some browser over another... but still using each of them doesn't really feel that different, they all basically do the same thing, display the web pages that I visit.

Maybe others are using the clients in such advanced ways that I know nothing about, I just use them mainly as game launchers and so that they keep the installed games up to date. (But in GOG's case, I prefer using offline installers for single-player games because it gives me independence, and running the client is just an extra step into running a game. I use the clients only if I have to, and for online multiplayer games.)

This pretty much. Playnite is the only launcher I use nowadays. Steam client gave me more issues than Galaxy surprising. Like there damn filter being broken for me till this day. Playnite is what DRM free client should be.

Windows Start Menu is the best launcher.

How is anything that takes a login not DRM?

You don't need to login with playnite.

You just need a cream for that.

While I can empathize with your frustration, you've already figured out that using Galaxy is still optional if you can do without achievements, multiplayer modes, offline single-player content, cloud saving, Twitch drops, and other features.

Many games available in this store can be played both online and offline just fine, even without Galaxy. In some cases, an additional launcher and a third-party website account are needed, and there are cases where games will not launch if you don't grant them outside access.

Regarding the error you've experienced, when does it occur? Is it at the end of the setup process? If you receive messages such as '...the client process can't be started...' or 'there was a misconfiguration... the client process could not be started...,' that's an indication that your Windows firewall or third-party security suite may be blocking access. To solve this issue, you need to unblock the files, close the error message, and start the app.

If the error occurs after the installation process has finished and on the first attempt to start the client, an error log should be created and stored in C:\ProgramData\GOG.com\Galaxy\logs. Please upload the file and provide a link or copy and paste its content so that more experienced members of this community can identify the source of this error and to be able to suggest to you steps to solve it.

In the meantime, here are some things you can try, in no particular order:
① Install any missing VC-redist packages or repair any that are already installed on your system.
② Check your Windows firewall or third-party antivirus apps to see if they are blocking access. Ensure that no files have been contained, quarantined, or deleted, and that outside traffic for client and helper services is allowed.
③ Start the setup process with elevated/administrative rights.
④ Download and use the latest offline installer package
⑤ Consider selecting a custom folder on your drive, such as [drive letter:]\Client\Galaxy, instead of the default path, which should normally work just fine. The default path is usually C:\Program Files (x86)\GOG Galaxy\ on a Windows system.

When opting for a custom path, AVOID installing anything in your system drive's root folder, such as C:\Galaxy, to prevent the risk of losing all your files and folders when uninstalling the client. ALWAYS opt for C:\mainDirectoryName\subDirectoryName instead, eg. C:\GOG\Galaxy

Clients should not be.

I'm sure you do you if you want to view your owned library, download/update your games, log achievements, interact w/ friends, you know... do client things.

If all you are doing is launching an already installed game then that's lame. Your desktop can already do that.