Noita tries to sync C:\Users\[USERNAME]\AppData\LocalLow\Nolla_Games_Noita\save_rec\ and my screen recordings takes up way too much space for that. Now the Galaxy version is essentially broken.

Is there any way I can just clear Noita's cloud data?

You have to delete the data, or move it somewhere else on your PC, when the game is running. Then exit the game, and if Galaxy isn't completely bugged it should sync with the empty folder.

"What happens in Internet, stays in Internet".

Just uninstall galaxy, win!

This is the correct answer. As long as you delete what is in the folder while the game is running, Galaxy should auto sync and empty folder on exit.

Thanks, I'm sure that would have worked, except ... I can't even start the game, since its stuck on sync.

You can disable cloud saving/syncing only for that specific game.
Good luck finding Orbs of True Knowledge ;)

Disabling sync is a nice feature! Nevertheless, I just scrapped Galaxy.

Speaking of orbs, I just found the the lava one, but with my sync screwup, no nuke spell unlock. Oh well, I'm finding nukes slightly distasteful!