@LostPlot This is your network diagram, I believe: I would like to suggest the following test: 1. Unplug Ethernet cable connecting Main Deco to the switch, from Main Deco and from the switch. 2. See...

@Rapo2 Check the following TP-Link KB article: https://community.tp-link.com/en/home/forum/topic/624082

@rodrigue741 That usually means Deco unable to negotiate gigabit speed on Ethernet link. That usually points at issues with cabling. There are multiple ways to test that theory, for example: 1. Swap...

@Jokker Good. It means wired link between Main Deco and router is without issues. I just helped someone with troubleshooting their WiFi speed related issues, so not to repeat myself I'll just link to...

@KenjiBailly You should return these if they don't meet your expectations. Two things to mention: 1. X20 is the most budget Deco model from X-series (WiFi6). These won't be speed daemons. Mid-range...

@Jokker Do you have asymmetrical Internet link, such as gigabit down/250Mbps up? This "Test Internet Speed" is speedtest over wired connection from Main Deco to the router. If you had symmetrical...