Are there any black or brown Zigbee or ZWave plugs?

[sidjohn1]

Yes,

ZW15R-1BW

Expand Features & Benefits for the color change kit part numbers. You’ll have to buy it in white and buy the color change kit. I went for black, for my use case it was worth it.

Also you’ll want the beta firmware ASAP

Anybody know where to get ZW15R / DZR15 - Leviton Receptacle Firmware?

I haven't ever heard anything about DZR15 f/w, but the ZW15R has a beta firmware available that helps with the issue of them dropping off the mesh. You need to email dssupport@leviton.com and ask them to help enroll you in the 15R beta. These steps work for both the other f/w files Leviton has publicly available and the 15R beta f/w.