Out of curiosity, is most of your exposure to people doing voice training for trans folks online?
My default assumption would be most providers are cis, but I have approximately zero exposure to online voice resources and my limited exposure to IRL professionals has been entirely cis people. (A quick google does not tell me whether the authors of The Voice Book for Trans and Non-Binary People are cis, which seems to be the “modern” book rec.)
Are you getting hormones from a doctor? You should be able to ask them for a referral, either for a scan or just to a specialist if they’re not the right person. (Unless there’s something specific requiring a specialist, breast health screening is often done by GPs/primary care, at least in the US.)