got-your-back uses Gmail's API instead of IMAP with an insecure app password, which is a discouraged way of accessing Gmail and will eventually be phased out in favor of OAuth access tokens over IMAP (in fact, I thought it already had been).

As for other services beyond Gmail, there's not a great ecosystem for exporting.

For one-off exports, Google Takeout is decent enough, although there's a lacking ecosystem to import the big .mbox files back to an email provider.

Looks handy, although it only grabbed like the first 2 years of gmail for me, out of 20. Re-running the docker image did not help.

What benefit does this have vs Google Takeout?

Nice but... Backup is nothing without restore and actually "restore" for third party services on a closed proprietary infra it's not possible...

My way for mails is simply having local maildirs using mails via notmuch and serving the maildir if needed via local dovecot/with an eventual MailPile/Rainloop etc webmails, for contacts Davis (like Radicale or Baikal) with DavX⁵ on Android etc, IOW the sole way I fond is being able to use someone else service if I need it (for instance not to end up in spam on all web giants mails) but still owning my infra. Just having data I can't really use it's not enough unfortunately...

Does the .eml file preserve Gmail labels? Does it handle the 'labels apply to messages not threads' problem?

I prefer an executable file to node.js garbage even if I have a Docker. Does anybody have a ready-to-use alternative that is not written on JS?