You can use kodi on any old computer or a kodi device like Vero that uses OSMC. There are non official apps for most services. Some take a little time setting up, others just username and password. While kodi its self might not spy. The streaming services certainly still track what you watch.

Depends on what your using it for? For 3d printers I like FreeCAD. Though it has a bit of an initial learning curve. It has a lot of functionally. SolveSpace was pretty good but I had some trouble with fillets and things. Might have been user errors… I havent used blender much but heard its good for more artistic modeling for games and videos. Not sure if it would work good for 3d parts? Anyone use it for that?

Two issues I have with them.

First the size. Being on a poor internet connection makes downloading them painful. Some apps are 200MB for the apt or a flatpak install 1.5GB! Also doesn’t help with disk space.

Second I often have issues saving files. Some apps use non standard folder location and some still save them to the non standard location even when you select one of you own. Block bench was bad. I’m not sure what causes this, if it wasn’t for the size I would probably spend more time looking for a fix.