Self hosted Office Suite?

Does anyone know of a multiuser office suite (like Google docs) that you can self host (like only office) that doesn't cost money. I can use libre office just fine and works great but if I want multiuser the only free thing I can find is Google workspace. I want to host it to just lan computers not to open Internet but I can't find anything. I don't want it to be on the cloud but even if it was like a game lan where someone had to be the "host" for the doc/spreadsheet then other people could edit is an option but running it on my server is preferred. I'm new to self hosting and getting proxmox with truenas scale and Ubuntu going.