Sidecar not working with OCLP (Used to work until I updated the OS, can't revert changes)

My old MacBook Air (Intel) sees my main Mac (M4 Pro) as an extended display option via AirPlay/Sidecar, but my main Mac doesn’t see the Air as an available device at all. Both are signed into the same iCloud account, on the same Wi-Fi network, with Bluetooth on.

Edit: Airdrop works both ways