https://9to5mac.com/2024/11/14/here-is-the-best-way-to-use-you-ipad-as-a-mobile-mac-mini-display/
..Method 1: iPad as dummy display
What you need:
MacOS computer
Any iPad wth USB-C (does not have to be the iPad Pro)
HDMI to USBC capture card (There are a few to choose from but this is the one i have tested that works 100% of the time)
Regular HDMI cable (Anker makes a great reliable one, or just use what you already have)
The Orion App (Its Free)..Method 2: Continuity
What you need:
Mac running the latest MacOS
iPad running the latest iPadOS
Both devices on signed into the same iCloud account
Both devices on the same wifi network
Both devices within 30 feet of each other (ideally)..
* Great mobile option for Mac Mini and any USB-C iPad.