I got the same issue. after I updated my note 10 plus yesterday, the miracast on my lexus nx200 doesn't work with note 10 plus. I can't believe this happens on such an expensive phone.
Samsung, pls sort.it out!
I've been connecting without flaw to a 7023B radio head with just the developer USB debug settings on before the Android 10 update on my S9. Hope they fix this soon.