Both‼️ Merriam Webster will tell you that equipt is the past participle of equip. So is equipped.
I suspect it’s much like learnt and spent vs learned and , uh, spent again. In the U.K. learnt is used instead of learned. Learnt is used in every country except the USA and parts of Canada. They use learned. Many people born before the seventies in certain parts of the USA say they remember writing learnt and equipt and it seemed to have faded away. Much like most countries say Zed and not Zee for the last letter of the romanised alphabet. Why does the USA say zee then? Because in 1835 the alphabet song came out and in the song they changed it to see to rhyme with “tell me what you think of me”. Prior to that it was Zed, but the song caught on and replaced Zed with Zee.