I just had the same issue, but you can click quick edit to change page template.
I have a child theme of 2024 and I have some PHP templates. How I assign the template to the page has changed in wordpress 6.5. You used to be able to go to the page, then under summary there was an option for page templates. Looks like its gone on pages that use my PHP templates. For normal pages template appears but only allows me to change to the WordPress block templates.
The fix for me any way is to use quick edit, then select my custom php template. Hope this helps someone, it took me a while to figure this out. lol
