I meant USB-C. Doh! Interesting info about its support for PCIe.
I’ve just finished reading a long thread about HDMI to composite adapters on avsforum.com.
This is the tail end. Upshot is that there may be a secret menu in later Rokus to set the output resolution. There is also a box called a VHD-HD2CV that will convert aspect ratios as well as HDMI to composite, but it is $200. The thread, though old, is an interesting read.
I’m away from home ATM, so will try the magic key combination on a new roku when I get back.