I would like to add all games being released on Steam but not on GOG.
Do you not trust us?

... uh, I get your point, but your examples fall flat. Both mentioned games are available on GOG, and Riftbreaker has received its third DLC a while back as well. And neither seem to have any outstanding issues.

Got a response from one of the devs. Apparently the person in charge is busy with other work and there's no ETA when the GOG version will be updated.

Forgetting an entire part of your customer base (small/big as it might be) is not professional.

Looks like some users having an issue with the new version of the game . link

GOG customers would likley to be busy with other things than paying them ... but unfortunately that is not possible anymore. It's still a pity that this behavior is actually legal :(

Well the joke's on them since I haven't gotten around to buying the game.

The developer released its last game here and is up to date, maybe there is a chance to update the game... maybe if other users post their petition on discord they will add the latest patch to GOG.

Owlboy DRM-free downloads are outdated on Humble as well. It's been bundled more than once (Indie Bundle 18 and Feb 2018 Monthly Bundle) so probably quite a lot of people own it there too.

Offworld Trading Company - The Europa Wager
Offworld Trading Company - Market Corrections
Offworld Trading Company - Interdimensional

They are finally on GOG.

Batman Arkham Knight received an update. Changelog says the 2022 movie skin was added. Haven't tested it myself.

Yeah that is the reason I decided to buy the game on GOG regardless, knowing it isn't the latest version. Namely, it seemed the latest version might be broken so at this point I don't necessarily even wish it would come to GOG.

Trail Out appears to be missing the Last Pursuit Update from the end of May.
Not entirely sure if it's justifiably absent due to the new additions revolving around multiplayer functionality only.

Well the GOG version has multiplayer according to store page (don't know if it also has cross play)

Arkham Knight just got the most recent patch, adding the skin from the Batman movie, so that can be removed.

Unfortunately, the previous update that automatically unlocked the Zur En Arrh and Anime Batman costumes is still missing, so it should remain on the list.