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@smlplee199.
Are you using all eight ports on the RT-AX88U? What firmware are you running on it? When was the last time you flashed the latest firmware and performed a full reset to factory defaults, without using a saved backup config file to secure the router and connect to your ISP? And, without plugging in a USB drive you used for amtm/scripts (if you're on RMerlin firmware)?
You may want to do an electrical reset. But before you do, I suggest you unplug anything you have in Ports 5-8 of your router. Now, unplug the power plug from the router and from the AC wall plug. Wait a few minutes and then power up the network again. After waiting for at least 10 to 15 minutes after the router has booted up, test. Are the speeds any better?
If the above made a difference, I suggest you buy a $30 8 Port switch and plug it into Ports 1-4 of your router. And then, plug in whatever else you need into the switch and Ports 2-4. Do not use Ports 5-8 at all.
If the above didn't make a difference and you haven't performed a full reset in a while, you may want to see if that helps first, before considering the final option.
I have an ASUS AX86U and contemplating the installation of Merlin firmware. The DDNS settings on the AX86U are limited to select dns providers. If I install Merlin, will I have more flexability (choices) with the DDNS Settings? Thanks in advance!
www.snbforums.com
After creating the checklists two weeks ago to save the pages with settings, I've made all the screenshots (I think at least) of all the relevant guides written by @L&LD and the very useful tip by @netware5. The only thing is, those guides are great, except when you'll be offline at least for a...
www.snbforums.com
www.snbforums.com
If none of the above suggestions work (please explore all the links I've provided), you may need a new router to handle your current network. The GT-AX6000 is a very stable and more powerful model than what you have now. You may use your old router as an AiMesh node, or, in Media Bridge mode (to connect as many distant wired capable client devices as you can, to take some load off the wireless side).
Hope this helps.