The 3921 is the Premiere+ (2nd version). It supports both the IR and WiFi Direct remotes. On the Roku accessories web page, that's the Simple Remote and the Voice Remote.
https://www.roku.com/products/accessories/player
Dan
Ultra (4640), Ultra (4670), Ultra (4800), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Nvidia Shield, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.
