I’ve thinking about ditching my Protonmail email address with Posteo since I need IMAP support (because I hate using the Protonmail app) and honestly paying for Proton Mail Plus didn’t worth the money because they are pushing me to buy the Protonmail Unlimited but I don’t need all those capabilities nor would I use them and the best alternative I’ve found is Posteo and honestly I like it, I even got CalDAV support which I didn’t have in Protonmail, but personally I don’t know anybody who use Posteo, so I post this here.
I signed up for an account after reading about it on this site: https://digdeeper.neocities.org/articles/email Using it via Thunderbird on the desktop and K9 mail on the phone, works well and has been reliable so far.
I think that page is a really nice starting point, but keep in mind that the criteria used for ranking prioritizes anonymity highly. Security and privacy aren’t the same as anonymity. If you’re looking for an address to use publically, anonymity is a non-issue so the rankings there won’t be meaningful to you. The writeups are still useful though.