Sucks big time.

so... start tor browser, create a protonmail address without a backup address, sign up, delete proton accunt again...?

nostr:nevent1qqsguqz89yzvuuk6kk8v0a6sk89kvcc90tl38amesq03lvfe09lj2zqpz3mhxue69uhkummnw3ezummcw3ezuer9wcpzqf4q9g9jd3f683uzwlqkfydy56n46a659mpfhaeuwgf65gz56z2fqvzqqqqqqyg53may

SimpleLogin or Addy.io worked for me.