User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:81.0) Gecko/20100101 Firefox/81.0

Steps to reproduce:

Version 78.3.3

1. open the config editor
2. set mail.identity.default.attachPgpKey to false
3. open account settings > End-to-end encryption
4. enable "Add my digital signature by default"
5. start a new email message
6. check if "Attach my public key" in the "Security" menu is disabled

Actual results:

The option "Attach my public key" is always enabled regardless of the value of mail.identity.default.attachPgpKey .

Expected results:

The option "Attach my public key" should reflect the value of mail.identity.default.attachPgpKey

Additionally, an option to customize if the public key should be attached by default could be made available in the account preferences section, next to the "Add my digital signature by default" option.

Tomorrow's development version should have this working.
We consider to backport to the stable 78 branch in the near future.

Thanks for the quick reply Kai and apologies for the duplicate.
Seems like I missed that one in my searches.