For me this worked:

Download https://developer.oculus.com/downloads/package/oculus-adb-drivers/ . Connect your Quest. Unzip drivers and go to Control Panel\Hardware and Sound\Devices and Printers. Open Quest properties, select Hardware, select "Unknown device" and again Properties(Device Function Summary). In new window select "Change settings". In new window select Driver, "Update Driver", "Browser my computer", choose folder with downloaded drivers and click "Let me pick...". Select "Show all devices", Have disk and install "Oculus Composite ADB interface". After that, SideQuest connected with no problem. As a side note, after switching Developer mode OR installing SideQuest my Quest Guardian limits and passthru works somehow different(not in a good way) - be careful. IMPORTANT! In Quest do NOT push "Allow"! Because if you click "Allow file transfer", Sidequest will lose connection.