Updated Tor Browser automatically to version 13 and now there are bookmarks for this forum?!?
There is also a new/another bookmark:
- on Other Bookmarks > Distros when opening a new tabs!
It seems that it has not affected all Distros?
Tor browser is based on Mozilla Firefox.
On Manjaro systems we have a package manjaro-browser-settings which contains default browser settings.
The links to Manjaro is not a new thing - it has been so for years.
If this is new to you could be that Tor reads those settings - 
- I don’t use Tor so I cannot say more …