weston and freerdp tested over a remote connection in piCore-11.x using the instructions above.
Although I cannot view a video in epiphany locally on an RPi4 (presumably due to being restricted to fkms, an RPi3 is OK with kms) - I can view one remotely with an RPi4 as the server.
eog and totem added to the repos to view images/videos in weston.
For the moment totem doesn't want to play videos, but they can be viewed in weston with: $ gst-launch-1.0 playbin uri=file:///mnt/mmcblk0p2/media/video/video_test.mp4
or
$ ffplay /mnt/mmcblk0p2/media/video/video_test.mp4