I have a MacBook Pro M1 + an old iPad 8 (which is 2 years old). I'm thinking, why not turn the iPad into a second display for the MacBook, I heard that's possible.
The internet says that in System Preferences -> Display on macOS when you connect the iPad, it should appear immediately. Didn't appear.
The internet says you can try updating (let's leave the question "why" aside, if this feature is several years old). I go to updates on the iPad, see a 3GB update, press "download and install", 5 minutes pass, the iPad shows an error "couldn't install update", and I repeat this several times to be sure. Naturally, it downloads those 3GB each time before attempting to install, what else.
The internet says this can happen if there's not enough storage. I have 14GB free. Well okay, I had to delete half the apps from the 32GB iPad. And, lo and behold, after about 20 minutes of installation, it worked. Updated, but didn't help. Display wasn't detected.
Turns out, I just need to sign in to iCloud. (Why? For what reason?).
It works in its own way too. Periodically disconnects, doesn't connect, wireless transfer sometimes turns into USB transfer and back, the mouse lags when you touch the edge of the screen on the iPad. In general, same as always.