I have a gmail account that I never used
One way might be to start using the account......that is probably why they rejected it
You could always start using your gmail address as your email address for Linux .org......that will at least get it started and then they may allow it.
I would see it as being unproductive......why have a gmail account if you are going to have a proton account ?
Protons reputation is based on the fact that they don't steal your information/data....whereas Gmail absolutely steals your information/personal data
I think all email providers are criminals. They tell lies. They take what is not theirs.
proton may well be the best of a bad lot. zoho mail is owned by an Indian corporation, but on the surface seem half ok
I note that proton has :
Mail Plus
€4.99
€3.99 /month
which is around $6.45 australian per month.....they charge for 12 months at €47.88 every 12 month ($77.20)
I just mention this if you want/need more storage.
I would not give another email address to them as a "recovery" address. I also would not give them my phone number.
What do I use ?.....gmail. I have come to the inescapable conclusion that they
already have all my info.
I have been a member of various forums since around 2011 and used gmail way back then...so my info is screwed.
I do not trust gmail (google) ....I am not sure I trust proton either.