The easiest way to test for grounding is to plug a shielded cable into the device and use a (low voltage) multimeter/continuity tester to see if there is continuity between the metal outer of the RJ45 and the earth on the mains plug (obviously when disconnected).

Meridian owner since 1992
Prime & PSU, Focal Elear headphones, Roon (ROCK 8Gi5 NUC), Explorer 1 & 2, F80. 200/203, various Sonos (via Roon).