How to use iMac2012 as secondary monitor for 2017 macbook pro?

Thanks. I did some research, target display mode is only supported in these few older models?

I'm also planning to get a new iMac, which comes with thunderbolt 3. Can I still use these 2020 iMacs as target display with a thunderbolt 3 to thunderbolt 3 cable?

Quote from site:

iMac models you can use

as a displayCable

you needPort you need

on your other MaciMac (27-inch, Late 2009)Mini DisplayPort to Mini DisplayPortMini DisplayPort or ThunderboltiMac (27-inch, Mid 2010)Mini DisplayPort to Mini DisplayPortMini DisplayPort or ThunderboltiMac (Mid 2011-Mid 2014)ThunderboltThunderbolt

iMac (Retina 5K, 27-inch, Late 2014) and later iMac models can’t be used as Target Display Mode displays.

source: https://applerepairstation.co.uk/Technical%20Desk/use-your-imac-as-a-display-with-target-display-mode/

Aw thats a bummer. I've this big screen iMac sitting on my desk, but I can't use it as a secondary screen while working on my macbook? Apple should add the feature back to their OS.