Greasy Fork

Seems interesting!
Just i can't install it on Waterfox Classic and with Greamonkey...
Seems don't like @match and prefer @include.

But maybe it's not interesting with Firefox / Waterfox ?:
Chrome show the Shadow Dom, the others not.

I wanted style the generic video player (this one you have when you ask to open a video in an other tab).
They don't have stylesheet and apparently only use shadow DOM.

You can edit the script manually if @include is better suited.

The script doesn't require specific UserScript/GM provider browser ewxtension, or specific web browser engine.

But FYI, the script was mainly designed within Firefox with Tampermonkey.

Thanks, but i need test for that...

Finally, i tested your script with Chrome and Tampermonkey.

For testing, i try to use it on the Top banner of Wayback Machine(yes, i know, i can close it...) :
'WE DID NOT WAGE THIS BATTLE JUST AROUND A WEBSITE' [Web.Archive]

In Stylus, this rule as no effect on the element inside the #shadow-root (closed):

/* TEST (to remove the top Banner) with your GM (not work)*/
#wm-ipp {
display: none !important;
}

Maybe it's due to the mention (closed) ?
I have read somewhere that there is too an (open) shadow...

Or maybe i forgot something.

It seems very difficult to catch these Shadow DOM.
And using Ublock Origin don't work on it .

Note:
This banner in shadow DOM is only visible with Chrome by example.
In Waterfox Classic there is not (or only classically exposed on their The Wayback Machine [Home Page] )