Assassin's Creed titles and a couple others from Ubisoft are also not compatible apparently:
https://www.polygon.com/2020/10/30/21542629/ubisoft-assassins-creed-backwards-compatibility-playstation-ps4-ps5
The Nintendo eShop rating Thread: http://gamrconnect.vgchartz.com/thread.php?id=237454
List as Google Doc: https://docs.google.com/spreadsheets/d/1aW2hXQT1TheElVS7z-F3pP-7nbqdrDqWNTxl6JoJWBY/edit?usp=sharing
The Steam/GOG key gifting thread: https://gamrconnect.vgchartz.com/thread/242024/the-steamgog-key-gifting-thread/1/