Did karate as a kid.. my opinion.. it’s a racket and the belt system is simply a way to keep you coming coming back and paying.
Did other martial arts late teens.. Wing Chun etc.. You may as well be learning dance moves. Mostly set moves with submissive students.
Mid 20s to now (52).. Boxing.. Absolutely still love it. If you take it seriously you will prob be the fittest person you know.
MMA.. not done it, but we get them coming along to our gym all the time.. Most are pretty unfit, but when they’re not injured from all that bending and twisting they do to each other, they will tie you in knots if you let them get you on the floor.
Personally I’d wholeheartedly recommend a good ABA boxing gym if they’ll let you train there.