I'm not in the position to compare them, as I have never used DevonThink before. You'd also need to compare DevonThink to Paperless-ngx, instead of comparing my iOS app, that is not yet feature complete and which is just one of many clients to access Paperless-ngx.
I'll have to look into how the flow with Authelia exactly looks like. I guess the forward auth flows of Caddy and Traefik shouldn't be too hard to cover. And that's something I'd also want personally: I'm using a similar forward auth mechanism using Traefik, that I currently have turned off because of the app.
The docs of the other integrations of Authelia I have not looked into yet.