@drewex I am also facing the same problem. 5ghz is a really fast giving me close 100mpbs ( I am on 100 Mbps plan) and 2.4ghz is pretty slow at 10-13 Mbps and if I just move out to back yard  , I also experience frequent disconnection. Had high hopes for this router but sadly this is not working to the expectation and most of my devices except for my note 8 supports only 2.4 Ghz.

@drewex so i just bought one as well. saw the same slow speeds with 2.4. I switched it to brodcast 802.11N only and the speed went up dramatically. by that I mean from the teens up to the 70s. my 5 peaks at 290 mbps which is good but I'm on a 500 plan. my bigger concern is that on a 500 mbps plan, my wired connection only gets 300 max. It should be above 400 for sure.

@JMik22 it's a hardware issue for sure. Been like that ever since I got mine a year ago.

JMik22 wrote

Just purchased from Walmart today. 5ghz is hitting 200mbps but on 2ghz I'm always around 5-10mbps no matter how close to the router. Firmware Version: 1.0.5 Build 20200825 Rel. 38196(5553) Hardware Version: Archer AX1500 v1.0 I hope there is a fix otherwise I will need to take this back and try a different device.

I am having same problem with my new RE505X (AX1500) Extender.

No improvement with latest firmware - 1.0.9 Build 20201013 Rel. 184524

Archer AX1500 Router's performance on both 5g and 2.4g are excellent.

Extender is 1/4 slower than the TP-Link Ax1500 router's 2.4 speed but 5g is comparable to the router's 5g.

Tech Support is involved but I doubt they have a solution. Problem appears to be wide spread with their

routers and extenders.

@drewex 

I have had 6 tplink routers in my house, all very good, in particular the TL-WR1043ND which worked excellent for years at home.
I bought my first Wifi6 router, the AX1500 Version 1 less than a year ago... the performance has been less than the 1043ND (which was only 450MBites).

Weeks trying to solve it and as I could not leave the kids without their classes nor me with my telework, I bought and installed momentarily the Huawei AX30 to get out of the way; it is very cheap .... It has almost no parameters, just connect, and the speed flew, it gives me the full speed of my ISP of 600 MBites on my mobile.

Then I tried to put the AX1500 as an access point and I still have the same problems of negligible speeds on 2MHz, and on 5 MHz very changeable... I have connected on the ethernet gateways and run iperf3, getting 940MBite and no tx/rx errors... so the wired network is fine... It is then the AX1500 that is very bad its WIFI... may be its firmware or Hardware... but as it has been so long without warning by TP-Link.... Even shortly after they released the AX1500 Version 1.2 it seems to me that there must be an error in the hardware and they are not willing to change all the equipment.