I would suggest porting to a Gigaset phone (e.g GS5) would be great.
A soon to be EU OS with an EU built phone sounds like a winning offering, and squarely in the " TRUSTWORTHINESS AND DATA SOVEREIGNTY" realm.
This would be a particularly credible project with a high chance of a successful outcome, given that @piggz has form.
Just needs some EU entity to front it, and some degree of buy in from Gigaset and Jolla.
(From my perspective the biggest single SFOS issue is that for the last N years, by the time a stable version is available, the Sony phone is discontinued, and they have sold so few that there is no significant 2nd hand supply. In a few months Jolla (& Sony) will move on to porting to the next phone, and leave this one with unresolvable issues. There has not been a commercially available, working, SFOS phone for years AFAIK)