The classic here for me is 'Bound to the Battle God' by Ruby Dixon. I'd call it more romantasy, but the Ice Planet Barbarians series is honestly more sci-fi than tribal fantasy. The core appeal isn't really about clans; it's about survival and the slow burn with an alien.
For actual tribal dynamics, I've had way more luck in Omegaverse and shifter fiction. 'The Tyrant Alpha's Rejected Mate' by Cate C. Wells has that fierce pack loyalty, though it's set in a modern-ish world. Historical settings give a stronger tribal vibe. 'A Heart of Blood and Ashes' by Milla Vane has warring clans, blood oaths, revenge—it's brutal and the loyalty to kin is everything. That's where you find the real friction between love and duty to the tribe.
I keep hearing about 'Transcendence' by Shay Savage for a prehistoric setting, but I've never clicked with it. The loyalty there is just to the couple, not a broader group.