Anyway
(SOLVED for me - posting just in case it helps)
I've been having the wi-fi "internet not available" issue for a solid week now on my UK Samsung Galaxy S7. Won't stay "connected" for more than a few minutes usage. All other devices seem fine.
The problem appears fixed (or at least the phone has remained happily working for several hours) after I:
Firstly: Went into settings -> apps -> (...) -> show system apps -> Bluetooth Share and first force stopped, then cleared data. (I found this suggested as a solution elsewhere. It did not appear to fix it for me - but I can't rule out the fact that it's involved.)
Secondly: Went to my wi-fi router's config and DHCP-reserved an IP address for the S7's MAC. I was careful to pick a *different* IP address from the one the phone was currently using. Rebooted router (which was required to apply the reservation), turned off the phone's wi-fi (I was actually connected via a different access point, not directly to the router), turned the wi-fi back on once the router was available.
I confirmed that the phone had picked up the new, different IP. No problems since!
Cheers.
