I haven't tested out my TT-30P to 14-50R adaptor yet (camping spots have been 50-amp only so far) and there is no neutral connection in the adaptor. Otherwise the cord looks just like a normal TT-30P to 14-50R an RV would use.

So theoretically, if used only for EV charging, you could cheap out and use 6-2 Romex instead of 6-3, but I didn't want to take any chances on issues in the future like hooking up an actual RV and having things go very, very bad. I'm no electrician but I did read about the adaptors here.

I have this one https://www.amazon.com/dp/B07HKLCXPJ/ref=cm_sw_r_apan_i_6A01P27RVETW3R5MEG56?_encoding=UTF8&psc=1

With this adapter coming in https://www.amazon.com/dp/B07XNSXWM4/ref=cm_sw_r_apan_i_4H5RQBKT5DXVZPT1K9PQ

We're planning to stay at the fernwood campground and they confirmed that's the plug they use, but they also have standard 110v outlets if needed. I'm planning to change the max current in vehicle to 16a or 13a just to be safe with a 110v. I'm still looking for a decently priced 5-15 plug to 14-50 receiver as I ran into the exact problem you mentioned.