Google decided to start using AI on your gmail mails. At first they ask you atleast if you are intrested.
Still in a bit it will most likely be enabled by default.
This means AI could be training on your mails. *BARF*
Which in turn means it could take info from your mails and send back to google, which is scary as fudge.

Decided to dump gmail, atleast start the migration process. First you need to find a good replacement.
I shoped around abit, Yahoo was a contender, Fastmail was another one...

Proton mail was an easy choice. Open source!
They have a free plan, which should be good enough for most. The plan i took was Unlimited which is like 12Euro a month.
You get several email address aliases, maby like smurfd_spam, smurfd_shop, smurfd_private or whatever. All mails go into the same mailbox though.

I did Not look into it being able to be used in Thunderbird however.
It is not available out of the box... You need their special App in your phone. You also need a bridge to be able to use it in Thunderbird.
They have one of those, available for Mac, Windows and Linux. Not BSD though. Fortunately there is a solution.
Hydroxide and fortunately it is available in pkg for Freebsd.

$ doas pkg install hydroxide
$ doas service hydroxide oneinit
Enter mail account id: your proton mail address
Password: your proton mail password
Bridge password: Here it will spit out a proton bridge password that you use in Thunderbird
  

Add this to your /etc/rc.conf

hydroxide_enable="YES"

Then start the service

$ doas service hydroxide start

Then in Thunderbird, you create a new account.
Enter your proton mail. Hit next.
It will then say: "Configuration found for a Microsoft Exchange server" pointing to hostname: 127.0.0.1
I think you just add another account if you have say 2 mail addresses, you want to be able to send with.
Works like a charm.
Thunderbird 147

$ freebsd-version
13.5-RELEASE-p8