@avniel No idea mate, I never installed the beta. If the unit still accepts the update I would install it.

@deechte check the PDF inside the zip file, there's a link to an update utility Edit: this one: https://www.tp-link.com/nl/support/download/deco-m9-plus/#Utility

It's here :-) https://www.tp-link.com/nl/support/download/deco-m9-plus/#Firmware

@TP-Link_Deco I think it had something to do with my Raspberry Pi4 connected directly to the Deco slave unit. Maybe it tried to get an IP from the Pi instead of the main router. I've moved the Pi and...

Expectations: "Very short time" --> yay! Reality: "Q3 2020" --> whut?! At least we've got some sort of timeframe now..

The Deco M9 Plus V1 got an update yesterday, maybe they are close finishing v2 as well? https://www.tp-link.com/nl/support/download/deco-m9-plus/v1/#Firmware