@Grease 

There is not a shut off switch, what you would do is set the category to standard. If you are seeing reduced speed, set your computer to high priority. Make sure the total speed on the upper portion has the max speed available for your internet connection.

Small office with 5 PCs all performing basic website activities and low performance requirements. SAME ISSUE -- QoS throttles random connections (both wired and wireless) causing very bad internet speeds as low as 5Mbps. Resolves via reboot but reoccurs within a 24hr period while QoS re-categorizes PC activity. Replace TPLINK AX6000 router with older NETGEAR AC1900/R7000 temporarily worked fine. This confirmed it is the TP-LINK AX6000 router and embedded auto-QoS is highly suspect. Tried to Telnet/SSH but no option to disable. Even blew away router config a few times, set device priority to standard, ensured all defaults were set, etc. but no luck. Only way to be sure is for TP-LINK to allow QoS to be disabled like 99% of the routers available today. I will need to move to NETGEAR where QoS options can be disabled by the user. Great hardware but major software development fail..

@ChrisVPN I was seeing similar behavior on my Archer AX6000 as well.  For me it turned out to be some issue with IPv6 and wasn't actually the QOS function messing things up.  I'm not sure you have IPv6 on but if you do and can test with it off give it a shot and see if it helps.  I was also having issues with random devices having DNS routing issues with IPv6 on so I tried CloudFire and it still had issues leading me to believe it is a firmware issue. My ISP doesn't publish their recommended IPv6 settings so I may one day contact them to see if maybe I had it setup incorrectly.  With standard IPv4 settings I have zero issues with the router but I'd prefer if I could get IPv6 sorted.