Comment # 6 on bug 1189811 from Fabian Vogt

(In reply to Robby Engelmann from comment #5)
> I mean, if I disable this Add-on:
> 
> Plasma Integration (disabled)
> Provides better integration with the KDE Plasma 5 desktop.
> 
> coming packaged in:
> plasma-browser-integration     | Helper for the KDE Plasma Browser Int... |
> 5.23.80git.20210927T195605~d9cfc2d8-ku.2.1 |

Ah, the plasma browser integration extension! That's also a separate process
though.

By uninstalling the package, you only removed the "native host" part, which
only disabled some parts of the browser extension. I assume this also doesn't
happen if you leave the package installed, but disable the extension in firefox
instead?