I use Readeck as well. My only complaint about Readeck is there really is no ‘one click, backup/export’ option. You can, however, download all the zip files it makes along with the db, and transfer it to another server. I know you can import bookmarks from Firefox, and you can export the epub, but you can’t export all of your saves. At least I’ve never found a way beyond just downloading the full db and zips.
Thanks for sharing OP. If I could find a selfhostable Notepad++ I’d be in high cotton. It ticks all the boxes I need.