Debian 9.3's gpg issue is driving me crazy! I can't install anything outside of the default apt repos no matter what I try.

No matter what, apt always does the exact same thing. It adds the repo; then finds, imports, and processes the key; and finally fails with "gpg: no valid OpenPGP data found."

I've spent hours looking this up and trying to fix it.

Just. ARGH!
☹

Mozilla really knows how to nudge one to not use email encryption by default.
Since Thunderbird has native support for OpenPGP encryption, i can only chose to encrypt all or no messages by default. There is no opportunistic mode and there are no per-reciepient encryption preferences. The Enigmail addon had both.
So i obviously have gone for encrypt-by-default.

But since then, whenever i want to send a message to the majority of my contacts, i have to manually disable the encryption or get annoyed by the no-key-found dialog.
I thought, i would get the muscle memory to just disable encryption for recipients for wich i don't expect to have a key.
But they also made the GUI so i have to open a dropdown and then click on the right item to do that. All the items basically look the same, as there is no color coding or specific icon for them. The item labels are also too long for unconscious pattern recognition.
So i didn't got that muscle memory.

I now have turned off encryption by default and will probably forget to enable it for some emails wich i actually could send encrypted...

Trainee accidentally said md5 is an encryption... Gave him the "functional specification of OpenPGP on ISO Smartcards". He learns OpenPGP now, before he reads that I hope.

OpenPGP or GPG?

++ first comment for OpenPGP, second for GPG (shameless ++ farming as well)

Post relevant fingerprints in comments if desired <3