World Aquatics tried that.
Swimming World Cup’s new ‘open’ category for transgender athletes scrapped as it received no entries
World Aquatics became the first major Olympic governing body to ban transgender women from the elite female category but, as part of last year’s announcement, had promised to stage events in a third ‘open’ category that would be separate from the usual men’s and women’s races.
The first opportunity for transgender swimmers to compete in this category was due this weekend, when the World Cup in Berlin was ready to host 50 metres and 100m races in each stroke, but not a single entry was received.
It suggests either that there is a minimal number of transgender swimmers who are willing or capable of competing at an elite level or that there is little desire to compete in races outside of the usual categories.
Or trans athletes want the validation of competing in sex category that they think matches their ‘acquired gender’.
https://archive.ph/ZwRLt