This is a plugin I found recently and really enjoy. It gives you the opportunity to redirect several webpages to alternatives. For example Youtube to FreeTube or Piped. If I search for youtube in Firefox, FreeTube automatically opens and shows me my feed. I like it, I use it, I can recommend it.
I would suggest Redirector.
It lets you redirect any site you desire.
Sadly the developer passed away. I found out after looking into the development when trying to edit some redirects brought my phone to its knees. It’s a good extension, but clearly needs a bit of love.
RIP Einar Egilsson
I use both, LibRedirect and Redirector for things that are not supported in LibRedirect.