Is it a secret Satellite?
No mention of what the Express-AM4 was launched to accomplish. It is quite a heavy one, though.
Right here in the OP:
“Express-AM4, built by Astrium Satellites of Europe with input from Russian industry, is a Eurostar 3000 satellite frame carrying 63 active transponders in Ku-, C-, L- and Ka-band. The two Ka-band transponders will be satellite fleet operator RSCCs first use of Ka-band for broadband communications links.”
It sounds like a pretty conventional comm satellite.