Buy European

AFAIK, you do need to change your email on all your accounts individually. However, you don't need to change all of them immediately. You can (and should) change over the most important accounts you have, and then you can set up a forward on your gmail adress, which then catches any less important accounts and forwards them to proton, and update those accounts once you remember they exist.

At this point in time your email is your identity. If you feel up to it, you can buy your own domain and set it up with proton or any other email provider. It won't help you just now, but if you want to move in the future it means you can change provider and emails will just go to the new location.

As others have said, you will need to switch other counts individually. Even if tools existed, would you want a 3rd party to know all the accounts you have?

That being said, you don't need to do it all immediately (as others also mentioned). What I did was change emails for my most important services and things I use often and made sure they were working (banks, gog, online shops etc.). Then I export all the emails I had in other accounts and imported into proton. I took that opportunity to sort things a bit but not really necessary. Then I set up forwarding from my other email accounts. I did this over my first few weeks with proton and now, if I happen to need an old account or notice emails are getting forwarded, I will switch those things. I can also see this in proton pass and if I notice an account has a sign in with an old email I'll try change it to the new on before doing stuff with it.

If you take it easy and just focus on getting forwarding working and ensuring your most use stuff is switched over then it's not too much of a ball ache

I think there are ways to forward emails?

When I switched to Tutanota I just kept my old account and moved stuff over as I decided it was important.

So now my gmail is mostly for spam and companies I don't trust lol