Want to use my 2015 iMac as a monitor for 2021 Macbook Pro with M1

Hey there!

It appears that the feature you're using is AirPlay to Mac:

Set up your Mac to be an AirPlay Receiver - Apple Support.

To use AirPlay to Mac, you need to have one of the following Mac computers, running macOS Monterey or later:

• • MacBook introduced in 2018 or later
  • MacBook Pro introduced in 2018 or later
  • MacBook Air introduced in 2018 or later
  • Mac mini introduced in 2020 or later
  • iMac introduced in 2019 or later
  • iMac Pro
  • Mac Pro introduced in 2019 or later
  • Mac Studio introduced in 2022 or later

From that list, it seems that only your 2021 MacBook Pro is compatible with AirPlay to Mac, not your 2015 iMac, regrettably. That's why you don't see your iMac on your MacBook Pro when you try to AirPlay.

Hope this helps!

-Jack

Continuity features and requirements on Apple devices - Apple Support

Set up your Mac to be an AirPlay Receiver - Apple Support

AirPlay from a Mac to an Apple TV set-top box goes way back. Your iMac can act as an AirPlay transmitter. AirPlay to a Mac is a much more recent feature. Your iMac is not new enough to act as an AirPlay Receiver using the built-in support in Monterey and later.

There may be third-party applications that would let your 2015 iMac act as an AirPlay receiver.

These probably would be using AirPlay v1, instead of AirPlay v2, thus restricting "resolution" to 1920x1080 pixels or less.

One of the other usual requests won’t work here.

The target iMac and the source MacBook Pro are both too new for Target Display Mode:

Use your iMac as a display with target display mode - Apple Support

MStouchbarapple wrote:

Sorry Not relevant with what I am looking for.

iMac 2015 isn’t going to work as an AirPlay receiver, as mentioned above.

Nor is TDM.

ARD/Screen Sharing: Share the screen of another Mac - Apple Support (HK)

AirPlay receiver: Set up your Mac to be an AirPlay Receiver - Apple Support (HK)

Re: “I have problem seeing imac listed on macbook pro which has mirroring support according to the support list.”

Your MBP is on the support list to be an AirPlay Receiver. Your iMac is not. Your iMac would need to be on that support list, and set up as an AirPlay Receiver, to show up as an AirPlay destination on the MBP.

Re: “By the way I can see in the mirroring list of macbook pro my other device (my 3rd macbook pro) which is from 2017.”

If you can AirPlay to a 2017 MBP, that’s an unsupported “Christmas present”, as the official cutoff point for a MBP to be an AirPlay Receiver is 2018 or later.

See If you can’t share Mac computer screens - Apple Support (HK)