webservers / the internet (nginx, databases, storage, networking, ...)
Mull / Librewolf
Nextcloud (contacts / calendar sync ...)
an email server and client
Matrix chat
LG WebOS on my TV
Home Assistant
lots of user applications
There isn't much important proprietary software in this apartment except maybe for the firmware of the dishwasher / microwave, washing machine and additionally whatever software runs in an old car.
I don't know about every component, but there is the Linux kernel and a lengthy list of open source components and licenses somewhere in the settings and manual. And you can get a busybox shell or something alike.