You can use Luma's force connection to a specific (slot A B C) APN.
Thank you @zbash92 this is working great for me on windows (kitkatslim) and linux (cutentr). btw I tested using latest ntrview for Wii U but flickers and lags a lot while playing.
From my experience Luma3DS' force connection doesn't work after you've been disconnected by the NFC patch, can't start new remote play session after that either. Generally need to enable NFC patch before starting a game.
I don't have Wii U to try ntrview sorry, but maybe you could try starting remote play after a game has started, setting it to one screen only, or lowering QoS value (say down to 5). Flickers usually happens with packet drops and lag is probably because of too many frames being sent in the queue. I've similar issues with UWPStreamer basically, albeit on Windows.