Well, the TV I'm using to set up the Beelink (a secondary 24" 1080p Samsung) is just using just a straight HDMI cable, no receiver or pass through boxes. This is also the same TV and HDMI cable I setup and tested several Beelink MINI MXIII's (S905) with Libreelec 7 and everything worked fine.
I'm also at a loss because it seems I've done everything correctly. I'll hook the Beelink up to my main Samsung TV tonight prior to trying anything else. My main setup is a Nvidia Shield TV with Kodi, and refresh switching works fine with that and my main TV. If refresh rate changing doesn't work with the Beelink and my main TV, i'll know it's in the box, since the chain works correctly now with the Shield TV.
Could you please post the output of these commands (use pastebin or similar):