I've been using K-9 instead. What am I missing out on?
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AfaIk there are no diffences between the same release of TB and K9, except a different 'branding'.
If I remember correctly, in a previous blog pretty, they started that k-9 would continue to be updated with the same functionality. There was something else other than branding that was going to be different but it wasn't consequential (at least not enough for me to remember).
Having been on K9 myself.
I checked my version # it was 8.0B and updated the 28th.
Installed Thunderbird because even the K9 site leads to it now.
Thunderbird app has a easy import via app, I just selected K9 import and re-sign into my provider ✅.
Isn't it the norm for the F-Droid versions of apps to lag behind the Google store counterparts?