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 ```