@trross33 and @dlang to be correct version 17.01.0-rc2 has the latest mwlwifi driver as per thread here WRT1900ACS v2 how to update mwlwifi driver
The radio is totally stable compared to rc1 but there is still an issue with the power table (a Linksys issue and not firmware) and signals are somewhat week. I have tested extensively and reported such to Linksys upon guidance received during this thread https://github.com/kaloz/mwlwifi/issues/139
Linksys reply was dismissive with crap of warranty voidance, when their sales pitch is OpenWRT, LEDE and now DD-WRT. Ironically they do press releases on such synergies too.
I have also used MetaGeek's Wi-Spy + Chanalyzer and can only deduce that the issue is the antennas but somehow the beam forming technology compensates a bit.
So go for the 17.01.0-rc2
I still have some issues though for example the channel on 5g band
config wifi-device 'radio0'
option type 'mac80211'
option hwmode '11a'
option path 'soc/soc:pcie-controller/pci0000:00/0000:00:01.0/0000:01:00$
option htmode 'VHT80'
option channel '104'
option country 'MT'
The channel is set to 104 but the router is using channel 36 instead.... have a look at the screenshot hereunder and see the Lumen WiFi 5g channel yourself. I reboot the system many times, but I can not get the channel to 104.