Sadly medical privacy and doctor-patient confidentiality seem to have become a thing of the past.
For perspective, electronic health records, AI and non-E2EE medical communications are recent erosions of privacy. There are public health insurance billing records, insurance companies, prescription records, mandatory reporting laws etc, all which vary wildly by jurisdiction, that may be worth considering too.
I cannot speak for you because I don’t know your medical conditions or logistics. I can’t add anything useful comments vis-a-vis Zoom, Proton Meet etc. If I could convince my doctor to do telehealth over Signal or my own Jitsi instance, I may try that. Most likely I would go to the clinic and consult with them physically, not do it over telehealth.
The general advice, even in the privacy community, seems to be seeking medical treatment without hesitation. However in my case I need to evaluate the risk of seeking vs. not seeking medical treatment. Without going into detail, without medical privacy, having a red-flag medical conditions or subpar general health on my record may become my death sentence.
If you are in the US, you could try seeing a medical clinic that is part of The Wedge of Health Freedom. They affirm patient privacy and support cash payments but I have no idea how far they go to protect patient privacy in practice.
Contrary to popular belief HIPAA does not protect patient privacy. This video by Naomi Brockwell (Youtube, Odysee, thread) explains the myth.