My example:
xfreerdp "$RDPW_FILE" /u:"$RDP_USERNAME" /p:"$RDP_PASSWORD" /sec:nla /cert:ignore +clipboard /multimon /monitors:0 /gateway:type:arm /network:auto /gfx:AVC444 /rfx /dynamic-resolution
Keep in mind that I was using for accessing Windows machine... Some flags might need to be a bit different
https://github.com/nixos/nixpkgs/blob/master/nixos/modules/services/hardware/amdvlk.nix#L13
Interesting, the option hardware.amdgpu.amdvlk.support32Bit.enable is there, but does not seem to be used anywhere.