This violates https://wiki.debian.org/DebianRepository/UseThirdParty, which states:

... The certificate MUST NOT be placed in /etc/apt/trusted.gpg.d or loaded by apt-key add.

If future updates to the certificate will be managed by an apt/dpkg package as recommended below, then it SHOULD be downloaded into /usr/share/keyrings using the same filename that will be provided by the package. If it will be managed locally , it SHOULD be downloaded into /etc/apt/keyrings instead.

Please update the instructions accordingly.

Maybe also take into account that Debian 13 and Ubuntu 24.04 will default to the s.c. "deb822" style *.sources files in favor of the old *.list files in /etc/apt/sources.list.d. See man 5 sources.list for the details.