[ThomasWaldmann]

Use an (old) iMac as an external display for an Apple Silicon Mac — free, no dongle, via Thunderbolt Bridge.

Apple dropped "Target Display Mode" in 2014 with the 5K iMac — and it never came back.

TargetBridge brings it back via software, streaming your screen to the iMac at up to 5K over a direct Thunderbolt cable.

Since v2.0.0, you can now even connect multiple iMacs to get multiple gorgeous 5K displays!

FOSS, under the MIT license.

Disclaimer: I am a project contributor, but not the original author of this project.