Note
No date is given for the latest update but this was released on Steam on 05 March 2020, and hit GOG Galaxy on 11 March 2020 (so yeah! for a month long delay in updating a standalone installer, and then only the Windows one).
There have also been 2 Hotfixes on Steam (6 March & 13 March 2020), but it's unclear if they're included, as the corresponding fixes aren't mentioned in the changelog, plus one of them was released after the date the game was updated on GOG Galaxy.

Changelog for Update 1.12

Changes / Alterations:
- Added reimbursement as new gameplay option
- Toggled OFF – trade-in value for locomotives only accounts for 50% at most
- Toggled ON –Balancing / Adjustment of price drops ( drops linearly down to 20% at most)
- Added the date until when the Journalist and & market crier remains active

Bug Fixes:
- Deleting a track rarely resulted in the creation of a track circuit
- Adjusted several achievements requests to the descriptives texts
- Fixed Crash issues caused by farms on the map “Northern Europe 1910”
- Dialogue window Town / Express Gowaods / Diagram: Colours are now correctly assigned to mail and passengers

Windows standalone installer, and those of all its DLC, updated (1.11.0.25273 ⇒ 1.12.0.25598): 10 April 2020.
Linux not updated yet.

EDIT: Linux standalone installer, and those of all its DLC, updated (1.11.0.25241-gog ⇒ 1.12.0.25598): 20 April 2020.