Sync is now a lemmy client anyway: https://play.google.com/...

There is already a FOSS stack exchange clone: https://codidact.org/

SE's DB schema is public (https://meta.stackexchange.com/...), and SE content is CC-by-SA 4.0 with database dumps regularly posted to archive.org: (https://archive.org/details/stackexchange).

All that is to say: there is a lot of groundwork done and the SE data could be ported over...

You might want to give https://mysudo.com/ a shot.

Shaddup and take my money!