You could do something like nextcloud to solve a lot of issues, but I’d still hesitate to recommend on-prem hardware and managing hardware yourself. It really comes down to the business tolerance for outages though, maybe the computers being down for a day or two doesn’t matter.
The lead lemmy devs are struggling with funding - https://join-lemmy.org/donate
Sync isn’t well updated / supported and I’d recommend moving to another client. I was a long time sync user so I found it hard, but I personally settled on Thunder https://play.google.com/store/apps/details?id=com.hjiangsu.thunder&hl=en_CA