wget -qO - https://download.jitsi.org/jitsi-key.gpg.key | apt-key add -
gpg: no valid OpenPGP data found.
And while updated
apt-get --allow-insecure-repositories update
...
...
E: Failed to fetch https://download.jitsi.org/stable/Packages Certificate verification failed:
The certificate is NOT trusted. The certificate chain uses expired certificate. Could not
handshake: Error in the certificate verification. [IP: 130.79.200.22 443]
root@meet:~# wget -v -O - https://download.jitsi.org/jitsi-key.gpg.key
--2020-05-30 12:11:57-- https://download.jitsi.org/jitsi-key.gpg.key
Resolving download.jitsi.org (download.jitsi.org)... 2001:660:2402::22, 130.79.200.22
Connecting to download.jitsi.org (download.jitsi.org)|2001:660:2402::22|:443... connected.
ERROR: The certificate of 'download.jitsi.org' is not trusted.
ERROR: The certificate of 'download.jitsi.org' has expired.
I would suggest the admins to use lets-encrypt for https. Any other solution does not work better, as you did not change the certificates as often and not automaticly.