Expired signing key for Tor Browser
It looks to me as if the certificate signing Tor Browser expired:
user@disp5457:~$ gpg --auto-key-locate nodefault,wkd --locate-keys torbrowser@torproject.org
gpg: key 4E2C6E8793298290: "Tor Browser Developers (signing key) <torbrowser@torproject.org>" not changed
gpg: Total number processed: 1
gpg: unchanged: 1
pub rsa4096 2014-12-15 [C] [expires: 2025-07-21]
EF6E286DDA85EA2A4BA7DE684E2C6E8793298290
uid [ unknown] Tor Browser Developers (signing key) <torbrowser@torproject.org>
user@disp5457:~$ gpg --list-options show-unusable-subkeys -k
/home/user/.gnupg/pubring.kbx
-----------------------------
pub rsa4096 2014-12-15 [C] [expires: 2025-07-21]
EF6E286DDA85EA2A4BA7DE684E2C6E8793298290
uid [ unknown] Tor Browser Developers (signing key) <torbrowser@torproject.org>
sub rsa4096 2014-12-15 [S] [revoked: 2015-08-26]
sub rsa4096 2018-05-26 [S] [expired: 2022-01-04]
sub rsa4096 2021-09-17 [S] [expired: 2023-09-17]
Note the expiry date on the [S]inging key.
Edited by Peter Gerber