I did the same thing last year, MoviesAnywhere is a complete gamechanger for digital movies being appealing. After doing some 4k streaming on a TCL, I got hooked buying 4k movies, since even if you have streaming services, there isn't as extensive a collection of 4k content as I'd like (and Netflix charges more for it). Disney Plus is the only service that has consistently offered 4k without upcharging.
The trade/sell movie code thread is a great place to look, too, especially since you just discovered it.
The MeWe communities and Blu-Ray forums are also great for buying codes and have a lot more activity than the thread here.