Calibre ui made me stay away, I don't mind different but sometimes you do need to get a bit more mainstream. Blender 2.80 did this move and it helped a lot I believe.

Check out Calibre-Web[1], It runs on top of a calibre database and some other calibre tooling, you can upload and download books from it, edit meta-data, read through the browser. Any books I grab I upload to it (can do via phone easily enough) and then I point my Kobo to it to grab books. I run it on a headless server, and never interact with Calibre UI.