TP-Link Archer C50 (EU) V6.0 - 5 GHz interface not present

I can update that the official Archer C50v4 firmware update 21.02.3 for the v5 too, but using for the V6 ( remember no 5ghz required just stability on the 2.4 ghz ) WITH WMM DISABLED updates fine using sysupgrade and shows no intermittent Wifi issues.

Side note: Since SQM is already installed, the so called WMM "QOS" feature may not be an ideal piece of code and there should be a way to enable "bn", ( WMM disabling just enabled "ag" at upto 20 MBPs tested ) and not try to do any QOS stuff on the Wifi interface. Funny that all OpenWRT routers with "abgn" and WMM enabled never really performed more than 20 Mbps ( even with WAN at 100 Mbps ) in six months of testing. So disabling WMM wasn't such a big deal when comparing Openwrt and Openwrt, even better at a steady 20mbps when assumedly WMM was not interfering with the speeds.

Another option is to try and test the official MTK wifi drivers:

Do not have the werewithal currently. Although it might be a good time to investigate Open Source code and developer team psychology.

Linux has been plagued with the "reputable developer syndrome" as in their code is only allowed to be built on and patched ever so slightly always tiptoeing around "developer reputation" and the like.

If we look at the angle that the original Openwrt open source driver was "booked for eternity" with a fixed amount of code, be it good intent or sheer inability to rewrite equally performant code in open source, or even employer and law forcing open source to write non-performant code so as not to appear to be copying the official code, be it closed or open, we have a problem.

It might be time for an open contest to invite corporates to donate code chunks as replacement for large sections of the code and a free for all forking culture so that main-line does not get booked by non-performant good intention or performant but commercially motivated bad intention code.

Basically the open source MTK wifi driver needs careful scrutiny and updating and this statement by Openwrt ( ): "

(Aug 2020): The cause for poor 2.4 GHz range experienced with some C50 v4 and probably C50 v5 models has been found. Also reports of random reboots OpenWrt forum Bug Report 2781 Fixed 2.4 GHz poor wifi speed (Feb 2021) from 19.07.7 mt76: mt7603: add additional EEPROM chip ID

certainly doesn't mention the WMM issue and certainly isn't all the problem with the MTK Openwrt driver.