And why do you use them?
Although I don't use them, the Jetbrains products should be near the top of the list.
DaVinci Resolve is THE video editor on Linux. Unfortunately the libre apps for it don't get even close, to the point that even with all the limitations in the free and paid versions, it still is the best option.
Also shout out to Bitwig Studio, although I don't use it.
Half-life: Alyx, Baldur's Gate 3, Elden Ring, ... you get the idea. It's not so much those apps per se, and I'd prefer them to be FLOSS too, rather it's the amazing content and in such rare cases, I'm happy to financially support the creators.
What aren't you happy to financially support creators of open source software you like?
My formulation wasn't clear, I meant to say I'm happy to support creators in general that make quality content, software or not, but I would always prefer to support open source, open hardware, remixable content, etc rather than closed and proprietary alternatives. I listed games as very rare examples where I'm still happy to support them even if I still wish that the software itself would be made open, even if delayed as Quake or Doom for examples have been. Does it make more sense now?
Never using proprietary software again. Maybe the only who can one be used be me and other foss' person could be steam..
Dungeondraft, Wonderdraft, FoundryVTT. Battle map making, world map making, and virtual table top respectively
I know you can't make battle maps with it but have you hear of azgaar ? It's an awesome open source world map maping web app !
When it comes to 2D CAD/CAM, then QCad is the best. They have a GPL version, but their commercial version has a lot more features, like importing/exporting most Autocad files, and CAM functionality. For just $40 bucks, it's worth every penny. The only disadvantage it has is that it can't ever have an ARM version, because the plugin they use for Autocad files is licensed, and it only exists for x86 afaik.
I like Insync. It synchronizes with Google Drive, OneDrive, and Dropbox. It is not the only client out there but it works better than the other ones I’ve used.