I was having an issue where my Windows 10 computer would not play HEVC h.265 video.

When you try to play the video, Windows Movies & TV app opens, but says it can not play it and that you need to purchase a $0.99 plugin from the Microsoft Store.

But there is actually a FREE version of codec that you can install/launch from the Microsoft Store as well (but of course they do not tell you about it).
Its called:

HEVC Video Extensions from Device Manufacturer
https://www.microsoft.com/en-us/p/hevc-video-extensions-from-device-manufacturer/9n4wgh0z6vhq

Alternate link:
https://www.microsoft.com/en-us/p/hevc-video-extensions-from-device-manufacturer/9n4wgh0z6vhq?irgwc=1&OCID=AID2000142_aff_7593_159229&tduid=%28ir__hwp9gz9pl9kftzgvkk0sohzize2ximz2ee93rrzl00%29%287593%29%28159229%29%28%29%28UUwpUdUnU56887YYwYg%29&irclickid=_hwp9gz9pl9kftzgvkk0sohzize2ximz2ee93rrzl00&activetab=pivot%3Aoverviewtab

Click the link above (its directly on Microsoft.com), choose GET, open the MICROSOFT STORE, choose INSTALL and then choose LAUNCH.
You do NOT need to sign up and do NOT need to create microsoft account to install this codec. Just skip/ignore any of those requests.

After this, try playing your HEVC h.265 videos with Windows Movies & TV app, and they should play!