Thimbleweed Park is available on so many platforms and services now. (Win (Steam/GOG, etc...), Linux, Mac, PS4, Xbox One, Switch, iOS, Android, etc...) There are achievements for nearly all the platforms/services that support achievements, except GOG Galaxy. Seems like a common occurrence for GOG to be a second-class citizen when it comes to them and whether or not one likes achievements or not, this is not a good trend to allow for a service wishing to compete with the rest.
Post about six months ago.
RonGilbert "I hope to add GOG achievements, but we’re really busy with iOS/Android/PS4/Switch that I don’t have the time. Once all that is done, I’ll look at it. Could be a few months. GOG has a framework, very similar to Steams. It’s not hard to do, it’s just some work and a bunch of QA. When we have some free time we’ll do it. Cloud saves on GOG as well."
When they finaly do it I will buy it from here.