Warning: An error occurred during the signature verification. The repository is not updated and the previous index files will be used.

[Gultak]

The Ubuntu repository uses an outdated key format which is no longer accepted:

Warning: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://ppa.launchpad.net/alessandro-strada/ppa/ubuntu noble InRelease: Sub-process /usr/bin/sqv returned an error code (1), error message is: Missing key <key>, which is needed to verify signature. Signing key on <key> is not bound:            Policy rejected asymmetric algorithm   because: RSA1024 is not considered secure since 2014-02-01T00:00:00Z

Please update your repository keys.

[Gultak]

After further research, it looks like my installation still uses an old key (the PPA page lists an RSA4096 key.

Now on to finding out how to update that :)

[Gultak]

Ubuntu removed the apt-key / apt-add-repository methods (they don't work any more in Testing).

Downloading the key as PGP/GPG as described in https://www.digitalocean.com/community/tutorials/how-to-handle-apt-key-and-add-apt-repository-deprecation-using-gpg-to-add-external-repositories-on-ubuntu-22-04 worked.