I'm using Debian Bookworm. If you use something like what is suggested in the instruction, for example:

``` deb http://geany.nightlybuilds.org/debian/bookworm stable main ```

`apt` will complain.

Your repository doesn't include `i386`. So you need to add `[arch=amd64]`:

``` deb [arch=amd64] http://geany.nightlybuilds.org/debian/bookworm stable main ```