Ownkeepass can read databases in kbdx encrypted format from other systems.
Does it not do the job?
I use ownkeepass successfully in multiple operating systems including Debian and SFOS in synchronized manner.
There is a native SFOS app named Sailsync Owncloud, but that refused to work some time ago. When that happened, I configured rclone to perform bi-directional synchronisation. There are Nextcloud clients available for the other mentioned operating systems.
I have a local microserver with openmediavault, a Debian fork that can be easily configured with smartphones via IP over the browser.
On SFOS for synchronization WunderFTP from openrepos is running in my local net and freefilesync running on Debian laptop syncs SFOS folders (media and other files such as Keepass db) with my microserver. I prefer this local solution.
Just coming looking for an equivalent of some random Android app is not very productive or a good way of describing things. Lot’s of people here are SFOS-only. Especially when you found other nominally similar apps that you didn’t want to use you really should try to provide some details of what you are after.