I’ve used one called CIFS Documents Provider in the past, worked very well.
It adds SMB/CIFS as a storage provider like Google Drive or Nextcloud to the Android built in file manager.
Available only from Play Store, AFAIK. And I think I was still on Android 14 last I used it.
Some months ago, I had UTD issues with Element X too. My hs has been up for some years, and the devs claimed they had done a lot to fix UTDs.
I was about to bring the server down, but as a last resort decided to log out all but one Element web session which was able to decrypt the messages and try resetting the key backup. Haven’t had any UTD issues since then.
Maybe worth a try.