TeXmacs repository on Debian 12 Bookworm

Hi community,

I was following this guide https://www.texmacs.org/tmweb/download/linux-repos.en.html#debian in order to install TeXmacs on Debian 12. I encounter with the following error after executing the step of “apt-get update”:

Err:6 http://ftp.texmacs.org/TeXmacs/tmftp/repos/apt stretch InRelease
   The following signatures were invalid: EXPKEYSIG 8CADE14440A2D6D6 TeXmacs Team <contact@texmacs.org>
Reading package list... Done
W: http://ftp.texmacs.org/TeXmacs/tmftp/repos/apt/dists/stretch/InRelease: Key is stored in legacy trusted.gpg keyring (/etc/apt/trusted.gpg), see the DEPRECATION section in apt-key(8) for details.
W: GPG Error: http://ftp.texmacs.org/TeXmacs/tmftp/repos/apt stretch InRelease: The following signatures were invalid: EXPKEYSIG 8CADE14440A2D6D6 TeXmacs Team <contact@texmacs.org>
E: The repository “http://ftp.texmacs.org/TeXmacs/tmftp/repos/apt stretch InRelease” is not signed.
N: It cannot be updated from a repository like this safely and is therefore disabled by default.
N: See the apt-secure(8) man page for details on creating repositories and configuring users.

What may be the procedure to sign the repository? What do you guys recommend.

Thank you for the help!

I am afraid that there might be no “official” build for Debian 12. You could use pjoyez’ builds instead: https://software.opensuse.org//download.html?project=home%3Aslowphil%3Atexmacs-devel&package=texmacs