Settings > Private browsing (under Privacy and security) > Open links in a private tab An alternative is to use Firefox Focus (Firefox Klar on F-Droid) as your

Settings > Private browsing (under Privacy and security) > Open links in a private tab An alternative is to use Firefox Focus (Firefox Klar on F-Droid) as your default browser, then its "open in" feature if you want to make it a permanent session.