I cannot see the item AIRPLAY RECEIVER in SHARE from SYSTEMPRREFERENCES

Yes, 4 years external monitors not work properly on mac mini 2018, now remove airplay options! THANK YOU APPLE FOR SUPPORT AND QUALITY!!

The AirPlay receiver option has been removed for Mac mini 2018 since Monterey 12.3.

According to Apple's documentation, actually it should never have worked on 2018 Mac mini models, even though curiously it was available from macOS version 12 to version 12.2.

Other viable options are AirServer or ShairPort Sync.