Klipper, for 3d printing. Most of current manufacturer use it as primary software for their printers.

Jami, a p2p zoom replacement I am looking to use.

I'll take a slight tangent to this topic and talk about FOSS software I've recently had to give up that I really really miss: Autokey. Autokey is a rough equivalent to AutoHotKey on Windows, it can do anything from on the fly text replacement (type teh and it will correct to the, or type *date and it fills in today's date) right up to firing whole Python scripts. it doesn't work on Wayland (apparently there are security features that prevent it from working the same way it does on X11?), and I've yet to find a replacement for it that does.

Ditto clipboard manager and altsnap with the Hot-click and fancyzone style controls

Image Toolbox Its a photo editor with everything you need. Its really really powerful and so fleshed out. Everytime I use it, I discover something new. The only sad thing is, that I can't donate in XMR otherwise I've would of donated. If you have an android, download it and try it. It's a must have on any phone imo.