Have you used the legacy editor for custom archives before?
The Query Filter options that you would use to add criteria such as which category of posts to include in the archive are not available in the block editor for custom archives, they are only available with the legacy editor (screenshot).
Actually, I didn't realise I could use Legacy with the archive pages and assumed that 'switch to classic editor' meant, switch to classic block editor rather than legacy editor.
I think I can actually boss it from here because the power is unlimited with legacy.