No I have the same problem on new note 10+.
In my case I have 2 router, when I turn off the wifi on first router and turn it on on the second , my note 10 stay connected to the wifi of the first router with esclamation mark indicating "connected without internet" (even if the wifi signal is gone) and not switch automatically on the second wifi router. I need to turn off wifi and on to the phone to refresh the new situation (i.e. the first wifi is gone and the new is on the second router).
I'm having the same issue, "internet may not be available" anytime I try to connect to wifi. Returning my phone tomorrow in hopes that a new phone will resolve the issue. If not I'll likely switch phones, this is unacceptable, as is Samsung's non response.
I have a Netgear Orbi setup as well, and have had all of the above issues - thankfully, connecting the S8 to the guest Network after opening it up to full access as described in the threads above did the trick! No issues at all 24 hours later.