Just to clarify a little, the link point to a publication dated on March 2019, where a leak of the signing key did occur.
Lately, the issue was not the same, the certificate passed it validity date and he get renewed (same key, but expire in 2024 now, if I'm not wrong )
seems it happend again ...
https://forum.yunohost.org/t/s…-of-apt-due-to-sury/15024
I have tested a few servers today and got the same error, fixed with:
and