Yes the previous iMacs sent a signal. Their current computers don’t receive the signal. This is not about the 5K display, you’re missing the core problem. It stopped working when the silicon line came out. You can’t get any iMac to work in target display mode on silicon Macs.
That’s not a technical limitation, that’s laziness. Go read more about this. It simply doesn’t work anymore without 3rd party solutions.
There is literally nothing stopping you from using a modern iMac as an external display using a thunderbolt connection today.
If you're OK with video compression artifacts, you can even do it over a WiFi connection.
You cannot grab an iMac, plug it into a silicon Mac, and get a picture on the iMac (without 3rd party software). This is incorrect. Please go look this up. The feature stopped working when silicon Mac’s came out. It only works on Intel Macs. 5K iMac or not.
Target display mode, the feature that allowed this, is no longer supported.
> without 3rd party software
At least you can finally acknowledge reality.
Also, VLC over a wired connection and streaming from one Mac to another using WiFi (AirPlay) are built into the OS.
I have already explained that and it’s not the same as native support any more than display link means one can claim M1’s run 2 external monitors (Mac mini excluded). I wrote this multiple comments ago:
> It simply doesn’t work anymore without 3rd party solutions.
https://news.ycombinator.com/item?id=50266629
You know what I am saying. This is a dumb argument and I’m moving on.