Questions on lxqt and networking

Dear all:

I have two questions, one for lxqt, and one for networking.

First, I am curious that whether the support of lxqt is available in nixos. Currently, I tried to install qt styles, but strangely none of them is available in the lxqt appearence setting. The only two available styles are Windows and Fusion. I would like to have kvantum-dark. I presume that this is because of some difference between the path in regular linux and nixos, but I just cannot figure out how to fix it.

Another question is about networking. Strangely, whenever I have both ethernet and wifi enabled, they just fight against each other and cause constant change in Internet interface. My corresponding configuration.nix code is:

  networking.useDHCP = false;
  networking.interfaces.enp0s31f6.useDHCP = true;
  networking.interfaces.wlp4s0.useDHCP = true;
  networking.networkmanager.enable = true; # Enables wireless support via NetworkManager

and I also add networkmanager into the extraGroup. What should I do to prevent these two interface from conflicting each other?