How to have page-{slug} files work with any theme

Hm.
Create a plugin,
Store your template files in the plugins directory,
Activate the plugin,
– check to see if a child theme exists
Copy the template files to the active theme

I think this makes sense to me.

See here under Sample Plugin :
https://wordpress.stackexchange.com/questions/312159/how-to-move-page-template-files-like-page-slug-php-to-a-sub-directory

Or, if you prefer, see here for having WordPress access a plugin directory for the page templates :
https://stackoverflow.com/questions/4647604/wp-use-file-in-plugin-directory-as-custom-page-template

For something a little more complex than you may like :
https://www.wpexplorer.com/wordpress-page-templates-plugin/

Thanks for the links…I feel like this would have been something done more often, but search results show me otherwise. I’ll give those a look to see if I can implement into my theme. Thanks

If it were me, I would take this approach :
https://wordpress.stackexchange.com/questions/312159/how-to-move-page-template-files-like-page-slug-php-to-a-sub-directory

I dunno, I’ve never heard of anyone doing this before!

I’m starting to think if I’m developing the theme for a client and I’ll likely maintain the site that having it work on any theme is not necessary. I don’t really want something I developed that isn’t meant for reproduction to be placed into another theme.

Ya, for sure. Seems like overkill to me.
None of my clients have Admin rights to their site anyway.
That’s intentional!!

Exactly, same here!