[qudat]

The main one that comes to mind is https://surf.suckless.org/

But there are many other minimal UI browsers as well as Firefox that support no tabs.

I’ve been using qutebrowser which doesn’t have much of a UI since it is vim based

[mo_42]

I like tab-less browsers. Leaving tab/window management to the OS means I don’t have to learn browser-specific commands on top of the OS's ones.

I'm using Firefox with a custom userChrome.css:

#TabsToolbar { visibility: collapse !important; }

Works quite ok but I cannot disable opening tabs completely in Firefox.