MaM and Geek and some other sites post a weekly 0-Day dump from the comic usenet boards.
So every week, all the comics for the week a dropped in one bundle. “0-Day Week” is what they’re called.
Make an feed in your usenet/torrent/autobrr client to auto dl these weekly packs. Then in mylar add it to the folder-monitor.
To “quickly” (processing takes a while) jumpstart a collection go to MaM and download entire years worth of comics and have mylar import them all.
Please use MaM as having seeders is really important for all these comics.
I personally use Tachiyomi or CDisplayEx if its on android. Or if it’s on my iPad then I use the paperback app using repos, or for my own collection I LOVE YAC reader. The guy who develops it is super cool and actually listens to requests when they make sense and it’s way better than Kavita or Komga IMO if you don’t mind using your PC as a server.
Edit: typos