venturta bluetooth pairing with iphone 6

Not sure what you mean here by "pair with iPhone 6." The Mac won't "pair" the same way it does, say, with a Bluetooth mouse, but an iPhone can be coherent with a Mac on Ventura with Bluetooth. For instance, we use Airdrop all the time to send/receive images between an iPhone 6 and computers on Ventura as well as Monterey.

I have an iPhone 7 IOS 15.7.7 and iPad iPadOS 16.5.1 (latest updates per 22/6/2023). Both can see my Mac OS Ventura 13.4.1 (so it is discoverable) in Bluetooth but are unable to pair. Error says "Mac with Ventura" is not supported.

Meanwhile my Mac with Ventura cannot even find nearby devices like my iPhone or iPad thus pairing is not possible. It will only find and connect to peripherals like head phones.