I do all document management with an app called DEVONthink. I’ve been working with digital paper apps for years, and DEVONthink absolutely crushes everything else. I put everything in it, and I sync it between devices using WebDAV via Seafile, which also works to get data offsite in case the house burns down. It’ll do encrypted databases, and it has mobile apps that work great. I scan documents directly into it, tag…
I used Evernote extensively for notes + going paperless. I was never comfortable and know better than storing private documents such as bank statements in Evernote (someone else’s computer aka cloud) but it was convenient and worked well.
I’m now slowly migrating Evernote content to Devonthink. It works extremely well, it is powerful and no subscription, it’s not cheap but as a dev I know development isn’t cheap and the price is justified for its functionality. Like you said you can get all the data you put in back out easily no lock in. Sure it’s not as shiny as newer hyped software but it works and is functional. I have some Hazel rules setup for example auto file downloaded statements.
What WebDAV server are you using? I tried NGinx but had issues as NGinx doesn’t fully support WebDAV, it was just that I already had a NGinx server running. WSGIWebDav seemed to work ok testing but not set it up properly yet on my NAS, wasn’t sure about trying Apache. My idea is to use WebDAV with all access via VPN to get same sync functionality as Evernote. WebDAV for syncing completely makes sense and was another reason I purchased it.