I use bypass paywalls clean on Mull by activating the Secret menu and choosing to install add-on from file. Works great for me.
Secret menu is in the About Mull page (tap on the logo 5 times) then back out to the settings pane to see some additional settings items added like install add-on from file.
How extensive of editing are we talking? If you just need some of the more basic features, there is Paint.NET which is surprisingly useful for a lot more than you'd think. Definitely not as feature-rich as Photoshop though.
I've not used it personally (I use Plex), but I have heard great things about Jellyfin. Does it maybe have the feature you need?
Jellyfin.org
I wasn't aware that we all had to adhere to YOUR standards of which softwares are useful/needed.
Sometimes people just want something. Maybe it doesn't align with what you want, but that doesn't make it wrong.