Hello. I use copyparty on my LAN hosting the kdbx file. It is exposed via webdav for my phone's client (keepassium). It is always available for KeePassXC (you can use rclone or just webdav in the file explorer). This is backed up to b2 every hour. I use WireGuard to access the LAN when I am not home. My phone autoconnects to WireGuard as soon as it is on any network that is not my home network.