My view on trans rights is that, in general, we should allow transgender people to do whatever it is they want to do. Use the preferred restroom, be referred to by their pronoun of choice, dress however they want, date whoever they want, marry whoever they want, etc.
When you specifically ask about sports it becomes a little more difficult because there is an actual advantage to be gained by competing as a biological male against women.
In that case, 1) it’s not always easy to evaluate biological sex. There is an athlete from South Africa (I think), who dominates women’s track meets. She was born female. But she’s probably intersex. She has elevated testosterone and a male body shape, but female genitalia. 2) Even if someone is born male and transitions to woman, where to they compete if they want to compete? It’s a genuinely difficult issue to solve.