EASA made a massive cock-up when they took over avionics certification, they had all the national authorities wind down their approvals capability for airborne handhelds, but never re-established their own approval facilities.
So the older ICOMs carry approval numbers based upon UK CAA approval from the 1980s and 1990s, but the A6E, which postdates EASA, does not.
I have an A6E, it's a super piece of kit. To use with a headset you need two add-ons, one is the headset adapter, the other is an external PTT. Buy a PTT on eBay, it's much cheaper than the official ones and works just as well. It does admittedly turn into a bit of a birds nest of cabling, but not dangerously so.
Mine is not registered with RCA, because without an approval number, I can't. It still works perfectly well without that however and if the authorities give me no route to be legal, what can I do about it? CAA won't pursue anybody for using an unapproved handheld because of the public embarrassement that this would cause.
G