Just certain ones. The flagging on the Xbox One version on TA should be fairly correct at this time, I checked it recently when it came up in someones list on UHH. By my reckoning, 84 of the achievements should still be possible.
I wrote a solution for many of the “community worlds” ones that are actually possible in Crossroads. It has some general advice that’s probably worth keeping in mind if you’re thinking of starting the game:
This and the other “Play x Minutes of Community Games” are still possible to unlock now that the Project Spark servers have closed. Here’s how you do it:
Firstly - getting Project Spark running in the first place without the servers is a bit of a challenge. I actually recommend taking your Xbox One offline (via Network in Settings), then starting up Spark and going into the Play menu, then going back online again. This will skip a lot of the timeouts and crap you’d otherwise need to wait through to get the game to the menus.
Once that’s done: any time you spend in Crossroads will count towards the time based Community achievements, but ONLY if you complete the quest and exit through the Exit Portal. If you quit out, it doesn’t seem to count this time towards the community achievements, but does count it towards the Crossroads specific achievements.