I took a whole day to check out all available FOSS options. KeePassXC won based on my criteria by a long shot.
One deadly reason against BitWarden (for me): Having a FOSS server that's not officially supported and more or less reverse engineered, is even worse than a proprietary API. It can become defunct at any point in time - and it might even be hard to catch it. At least, with 1P, when they deprecated their old Apps, they announced it.
Not saying that BitWarden is bad in any way. Just saying that the KeePassXC stack is FOSS all the way with no lock in and multiple implementations of the Keepass file format.
As for the SNAP package: I'm not versed in that. I'm just using the regular Debian package. Works fine for me.