How to prevent a folder being backed up in Photos but still seen in a gallery app?
You're not restricted by Google to use only Photos app as a Gallery app, so why not try a third-party app? I remembered that I used to use Piktures and QuickPic app and both of them (paid feature in Piktures), as I tested now, provides an option to show hidden or .nomedia file containing folders inside their settings. I'm sure some other gallery apps might be having a similar feature.