I was poking around recently. Adoption appears very low on a per-domain basis [1], but high-volume mail providers like Gmail support it.

Relatedly, DNSSEC adoption (and presumably DANE) is finally decreasing. So MTA-STS looks like the path forward. Lots of folks have been predicting this. [2]

[1] https://www.uriports.com/blog/mta-sts-survey-2024/

[2] https://www.verisign.com/en_US/company-information/verisign-...