Protonmail supports receiving a verification code by email. Use a disposable email provider that isn't blocked to receive the code. I _just_ made a protonmail account to test.
https://10minutemail.net/ worked for me just now.
https://10minutemail.com did not work as protonmail recognized the address I got from it as being temporary.
Hope that helps.
Matt
I already had it solved but I tipped a friend about https://10minutemail.net and it worked for him, for which he thanks you. I wonder how long it will take Protonmail to close this loophole :)