To be clear, the fwupd interface is not implicit, so it is not provided by the snapd / core snaps, and you would need to connect the fwupd plug you have in your snap to some other snap which is providing the fwupd slot.
The browser-support interface is implicit however, so the plug can always be connected to the snapd / core snap slots. However to get the sys/devices/virtual/dmi/id/product_name access through the browser-support interface, you need to use the allow-sandbox: true attribute with the plug declaration in your snap as in :
plugs:
browser-support-with-sandbox:
allow-sandbox: true
hooks:
configure:
plugs:
- browser-support-with-sandbox
though I agree with @ogra the ideal solution here is just to move that read access to something like hardware-observe instead.