New sysadmin module solution is now available in testing
Please try it out, gently, and if there’s no errors, then we’ll likely automate this as the new default (so the next time a general module update is done, the problem will quietly disappear 
)
$ sudo fwconsole ma downloadinstall sysadmin --tag=17.0.2.35
$ sudo fwconsole sa disable-deb-update-v13
$ apt-add-repository -L | grep stable
…that last command should show no output. Please let us know if that is not the case for you! Supplying your sources.list file(s) and filenames in pastebin.freepbx.org – then sharing the links in your replies – would help a lot, too. 
Finally, after those commands, your next apt update should show no nudges to update to Debian 13. (This change should stick until our planned release of an inline-upgrade tool next year to assist with FreePBX 17 on Debian 12 → FreePBX 18 on Debian 13 conversions.)