sharing App window on macbook to other device

Hi,

sidecar seems to be parked for no further development so I'm looking for an app that could share a portrait orientation Macbook screen on an iPad or better still to allow sharing an app window, or part of a screen easily between devices, if they can share a portrait phone onto the mac sure they could do this the other way.

I wish Apple would concentrate on innovative product functionality instead of new text icons.

Here's hoping one of you has seen something to help me.

Thanks