I would like to keep using my iMac (macOS High Sierra 10.13.6) as an external monitor for my Macbook Pro 2017 (macOS Monterey 12.4). Now, when plugging in the Thunderbolt Cable to the iMac and clicking F2 the iMac will restart and it won't show the Macbook's display, as desired.
"The other Mac that you're connecting it to must have been introduced in 2019 or earlier and have macOS Catalina or earlier installed."
From: Use your iMac as a display with target display mode - Apple Support
"The other Mac that you're connecting it to must have been introduced in 2019 or earlier and have macOS Catalina or earlier installed."
From: Use your iMac as a display with target display mode - Apple Support
Solve iMac restarting when clicking F2 using Thunderbolt Cable to use as an external display
