With just Samsung T7 500GB SSD (1 partition) and USB stick (Sandisk Ultra Fit 64GB) inserted--both as exFAT--my mY (2020.36.11) via a Anker USB 3.0 Hub showed 5 USB devices with the bottom one cutoff in the display with no way to scroll, regardless of insertion order. Removing the SSD would allow me to play music, but reinserting SSD caused same issue.
Lo and behold, reboot (hold down both thumb wheel buttons for 20s) fixed the issue. Now only 2 USB devices show, with the option to "change" the USB device, rather than having a vertical list. Also, it recognized music stored in SSD under "_Music" (with underscore), so naming requirement is apparently more lenient as well.