Here is a work-around that has seemingly resolved my periodic internet-drop-despite-appearance-of-sustained-wifi-connection on my ‘18 Pro 11”:
go to:
Settings->Privacy->Location Services->System Services (all the way at bottom)->Wifi Networking & Bluetooth (set to OFF)
Initially I noticed turning off Location Serviced and Bluetooth both. . seemed to ‘resolve’ the issue, then I started tinkering with settings more and found bluetooth on, location services on (with above noted System Services sub-setting toggled off) allowed reliable sustained wifi.
I am still testing, but after about 2 hours i’ve had no wifi hiccups. Previously it was happening easily every 15 min. Noting here that when internet connectivity did die, a simple wifi on/off brought it back to life.
I haven’t introduced sub-C connections into the mix yet to see if there is any impact. . awaiting delivery of my headphone dongle.