Proton's easy switch will automatically import your emails on the new account. Then you can setup email forwarding to the proton address. I recommend getting a custom domain. Otherwise, if you again try to change the provider, you'll have to go through the same hassle.
I used to like Skiff a lot. But they were acquired by Notion all of a sudden. Then I had to change email of my every single online accounts. Had to go to the banks multiple times. Still haven't managed access to some websites.