I deleted my proton account about a year ago when I saw that I could not login from tor anymore, kudos to tutanota for allowing to register/login without a cell phone it must be really challenging !
My solution - crappy china phone and the cheapest pre-paid sim card I can find. I turn it on, receive my SMS, then turn it off again. Doesn't track back to me because I paid cash, doesn't report my location because china phones don't have GPS, isn't on the VOIP or multiuser blacklist because its a "real" phone number.
It won't protect you against three letter agencies - it is more my double middle finger to everyone who thinks SMS verification has value, or somehow the gateway to marketing to me, or being able to harass me if they wanted. I have the telco turn off voice mail on the number so that nobody can produce phone records showing a completed call and say I was contacted.
Just FYI for anyone having this issue, Tor 2.0 is deprecated and has been hit or miss for roughly the past year. As long as you're using their Tor 3.0 onion address you should have few issues.
https://www.aliexpress.com/wholesale?trafficChannel=main&d=y...