@ecs0set wrote:
"Of the Composite connecting devices that will stream, mirror, or accept casting, none are currently Roku"
Are you saying that you cannot cast from an Android phone to a Roku device which supports composite, such as the 3910R? Sources I've seen suggest that you can, e.g. https://streamersworld.com/cast-android-roku/
PS. I appreciate you are trying to help - FYI I am also an I.T. professional and you can be assured that I have considered my requirements carefully! I am only trying to establish whether the 3910R WAS (I know it is not currently) sold in the UK so that I can determine if they MAY come up on eBay at some point in the future.
Late response - The 3910 does support Miracast-based mirroring, and as of OS10-4195 and RokuCast 1.9.6 it also supports it in Composite output mode (previously it did not: https://support.roku.com/article/208754928)
Additionally as of OS10-4195 (and AirPlay 1.14.104) it supports AirPlay2 (casting & mirroring), in both HDMI and Composite mode.
DIAL and Play-on-Roku based casting also work in both HDMI and Composite mode.