[Anonyma'am]

I seem to have an app that has no uninstall button (Online Plus), which infuriates me.

Does anyone know of an ultra-deep uninstaller that will scrub this out? I have Revo, but it doesn't even detect it: I can only see it in Settings/Apps.

I'm not an Android superuser and I'm legally blind so reading long articles exhausts me. AFAIK the next step is uninstall everything or do a factory reset - which I *really* don't want to do.

Android 8.1.0

Most uninstallers doesn`t do anything more than what you can do by manually uninstall app via info section.
For your problem,
First go to device settings and search for "device admin apps" and check if online plus is there. If it is then disable it and try to uninstall.

You can uninstall every app via adb. google for "debloat adb packages"

Wdym legally blind?
U seem to be an avid smartphone user?!