I had the same issue and found something that worked. Go into the BIOS and change “USB Dual Role Device” from “DRD” to “XHCI”.

To test: From powered off status, press Vol+ and power, continue to hold Vol+ until you see the selection screen - choose “Setup Utility”. Within the utility go down to “Advanced” > “USB Configuration” > select “XHCI” > then save and exit.

I am guessing this could be fixed on the software side since my old Deck is set to “DRD”, but has no issues mounting devices…someone above my pay grade will need to chime in on the “why”, but my guess is the new chipset behaves differently.

Per Apple: “With 80% Limit enabled, your iPhone will occasionally charge to 100 percent to maintain accurate battery state-of-charge estimates.”

https://support.apple.com/en-us/HT210512