I just followed the instructions on the https://openmodelica.org/download/download-linux page.

On Ubuntu 21.10, adding the GPG key of the repository with

wget -q http://build.openmodelica.org/apt/openmodelica.asc -O- | sudo apt-key add - 

yields a deprecation message. Indeed, the man page (https://manpages.ubuntu.com/manpages/im … key.8.html ) specifies that apt-key will be removed after Debian 11 and Ubuntu 22.04.

I'm not familiar with repository signing, but I found a blog post from Jan 2021 which explains quite well the security issue of apt-key and the new recommended way : https://www.linuxuprising.com/2021/01/a … o-add.html . It seems that the sources.list file should contain a new signed-by option like

deb [signed-by=/path/to/openmodelica-key.gpg] ...

So the present install instructions are still working, but it seems it will need an update in the coming months.
As of now (Jan 2022), it seems that apt-key is still in Debian testing (https://packages.debian.org/bookworm/amd64/apt/filelist ) but if the deprecation message gets fulfilled, it should disappear at some point before Debian 12 release (this resonates with the platform stability issue discussed in previous thread). Same for Ubuntu 22.10.