My heart sank when I read this.
Yes, Strongbox really is great. So of course it had to be “acquired” and will, eventually, bleed to death, which will probably take the form of an initial price hike and/or forced sub. It’s just so sad how everything turns to shit just as it’s getting good because of course the dev wants to capitalise and reduce costs.
Strongbox has no backend but what you provide yourself, except for the optional sync. That’s part of what makes it great, of course.
I’m not migrating again unless there’s a clear need. But my next stop, should it prove necessary, will probably be BitWarden with a self-hosted VaultWarden backend.