Problem with PGP encrypted titles

[papiche]

• Thunderbird version: 115.6.0 (64 bits)
• Thunderbird Conversation version: 4.1.6
• Operating System:

NAME="Linux Mint"
VERSION="20.2 (Uma)"
ID=linuxmint
ID_LIKE=ubuntu
PRETTY_NAME="Linux Mint 20.2"
VERSION_ID="20.2"
HOME_URL="https://www.linuxmint.com/"
SUPPORT_URL="https://forums.linuxmint.com/"
BUG_REPORT_URL="http://linuxmint-troubleshooting-guide.readthedocs.io/en/latest/"
PRIVACY_POLICY_URL="https://www.linuxmint.com/"
VERSION_CODENAME=uma
UBUNTU_CODENAME=focal

What did you do?
Use end to end encryption

What did you expect to happen?
Title being decrypted

What actually happened?
are replaced with RE: ...

[Standard8]

Given that I still haven't got around to completing encryption support alongside 115 (its complicated & difficult), I'm not surprised this is broken. Marking as duplicate of #2006 which is the work to implement that.