Indeed @Eric, Discover works fine on the Nexus 7 in phone mode. I do not have other wireless remotes, but I did a few tests yesterday:
I changed the density setting of my Nexus 7 (from 320 to 240 dpi) as described in this post:
https://community.roonlabs.com/t/lenovo-yoga-stuck-in-portrait/10749/33
With this change Roon starts in tablet mode. When I open the Discover screen, now it is slow as well. It takes even a bit longer than on the Pixel C, probably caused by the more limited resources.
Then I switched to the network. I made a direct wired connection from the PC to the router (Linksys E2000), no change.
Next was the WiFi. I switched from Mixed to N-only, from 2.4 GHz to 5 GHz, tried different channels but no change in performance. Typical distance from tablet to router is 4 meters, also tried within a meter but no change. The reported link speed on the tablet is 144 Mbps.
Also tested the WiFi performance by viewing a video on YouTube, typical quality is 1080p50 sometimes switching back to 720p50.
Should this performance be sufficient for the images transfer?
I will send you the requested logs later today.