When I select a hyperlink in a non-browser app, my default browser automatically launches to handle that link. Is there a way to instead show a "Select browser" dialogue box for it, where Iā can choose whether I want to open that link through Firefox, Brave, Tor, etc.?
Similarly to Android when no default browser is selected. Perhaps a 3rd-party app that does that sort of thing, like LinkSheet for Android?
There is something ... it is some kind of Launcher or Chooser. I have the Picture in my Mind but unfortunately, I don't remember the Name. And I'm not sure if it was a Gnome Extension or not ...
Click on 
from panel, click on settings.
Scroll down and click on default applications.
From here, you can choose which web browser you want launched from default.
If this solves your issue, please mark my post for solution solved.
It's not changing the default app, but rather having no default app altogether, so that when a link is supposed to be opened from a 3rd-party app, I'm given the option to choose which browser to handle that link.
Take a look here:
https://unix.stackexchange.com/questions/487203/choose-which-browser-to-open-link-in
You can create a script:
Here is a app that looks if it can do what you want to do:
JUNCTION, DANKE! Yes, that was what I meant! I couldn't sleep the whole Night because I didn't came to the Name.
@axylox: You should take a Look at this.
Junction is perfect! Thanks for the great suggestion, and thanks to everyone as well for the help. Not very tech-savvy to the point of coding it myself though 
As you know by now, no flatpak (or snap) on any system of mine!
