Protonmail has a BTC wallet?!
Yup it's Bitcoin-only Layer-1-only tied to your email.
So now all I need is your email and I can see all your transactions. They claim it makes a new address, but this is propaganda if the input/outputs are being used together. This is the worst of both email and Bitcoin privacy.
You shouldn't be using a web app in a browser for your L1 Bitcoin, it should be in a local wallet like Electrum. Just like their email, you don't know what's going on in the cloud. They write "not your keys, not your coins", but they don't even let you use your own PGP key for email.
Further, they called everything else other than Bitcoin a shitcoin. Even if we ignore Monero, they still don't even accept lightning for their vpn/email. Lightning is far better at privacy than L1, and more economical.
This shows they are basically a honeypot propaganda outlet, with a World Economic Forum rep on their board, that hands over thousands of emails a year. Now they can add bitcoin transactions to give context to those compromised emails.
Once again, I urge you to consider self-hosting your email. Any small VPS is barely more money than proton's paid plans, and we have cheap plans to set it up for you if you're uninterested in reading technical docs, https://simplifiedprivacy.com/email-cloud-combo/index.html
Stop living in web apps. You can really be self-sovereign.