j@mastodon (jcast@mastodon.social)'s status on Tuesday, 05-Nov-2024 07:11:14 JST

@erAck @zaunkoenig @tinx @thunderbird @fdroidorg

It's a metadata issue.
But to be honest, apart from the branding there is little difference now.
They claim the code base is the same, but there are a ton of UX differences from v.6 to v.8 which make it IMO slower and less usable.

To move from K9 to Thunderbird:
Export settings from K9,
Import from TB

Reenter all the passwords.
Quite seamless.