Which means any advanced user that did a proper, more secure PGP setup, can also not use PGP with Thunderbird for the time being.
For a friend of mine, setting up Thunderbird to use external GnuPG on Windows made it outright crash whenever trying to open a PGP encrypted email!
On one hand, Mozilla was cool enough to include (some) PGP in Thunderbird which in theory makes it more accessible as you can generate and use keys with a few clicks, which is also good for us advanced users as we can then email privately with friends that would otherwise be unable to use PGP.
Honestly, my advice to anyone that uses Thunderbird and depends on advanced PGP (smartcard etc.) for now: Just downgrade to Thunderbird 68.x and install Enigmail.