This whole issue for me has a simple solution. When these basic, rational and common sensical conditions are met I have no problems with transgender people competing in either of the gender categories that may potentially differ from their biological gender at birth.
1. First condition and the most important one - we need to see transgender males/boys competing with similar parity against cisgender males/boys. Right now this is only working one way - transgender females (humans born with male sex organs) have transitioned to compete with prominent and highly successful results vs cisgender women/girls, but not the other way around. I don't even want to get into the obvious reasons why this is because we all know them, so let's take that out of it. When we see evidence of transgender males having the same level of success as transgender females that's the first step.
2) Second condition, the transgender athletes in terms of competitive level need to be represented across the spectrum of abilities and performance in their new chosen gender category. So, we can't have a case where all transgender females instantly are all right at the top of their new gender category (case in point Lia Thomas, Andraya Yearwood) or conversely right at the bottom (no evidence/cases of this as yet) as I would hypothesize would have if a transgender male wanted to compete in a competitive realm vs cisgender males.
I actually thought a lot about this while running yesterday and tried to find a way that the above would be unfair, discriminatory etc etc - I couldn't. If someone can then I'm all for hearing it. End of the day if the underlying narrative here is equality, then to me basic conditions of equality must be seen to exist in both directions involving all transgender athletes.
Currently this isn't transgender rights issue, it's been highjacked to leverage an odd quasi female rights issue. The front is "transgender discrimination", the actual is "women are free to do what they choose - even transgender women, and that includes competitive sport too". Ironically though, it's backfired because it's completely infringed on the the vast majority of cisgender girls/women and their rights to compete equitably in competitive sports. But of course supporters of this don't really care because for them it actually never was about equality or rights to begin with anyway.
Anyway. back to the first points because I could easily have missed a connection - what would be unfair or discriminatory about establishing this first before this becomes a non-issue status quo?