Before you start going oh god why would you copy such an existing character blah blah, this guy actually has a backstory: just as shinzon was cloned by the romulans, Riker was cloned by the borg, but actually combined with borg tech. There are actually many more Riker borg clones but only this one got liberated. For now anyway.
So yeah, I tried to copy riker as much as I could with the char creator and added borg features. It's a bit difficult to get it right because the things that make jonathan Frakes Stand out are not available in the creator: the haircut, the portruding cranium, the portruding eyes and the long ears.. but yeah I tried to get it right.
The Cardassian Government & their expert Vorta/Founder handlers on Lazon II (in the process of reconstructing Thomas' baffling origins,) experimented with assorted P.O.W.s & their DNA to create expendable Starfleet/Klingon/Romulan/Jem Hadar drone/augment "Alpha"'s against the Borg as a "final solution".
The Dominion-Cardassian Alliance attacked Chal and raided the Shatnerverse world's lab-bunkers chock full of TOS/TMP-era genetic research, took hand-selected citizens as POW's and tried unsuccessfully to hold the site as one of several candidates for the construction of Semptok Nor.
Cloned Riker? When did the Borg get a chance to clone him? Looking at this, I was thinking the Riker from "...the Borg are everywhere!" universe from Parallels would be more believable. The cube he's on get's itself "lost" during a failed attempt by the Borg in that universe to crossover and invade other quantum realities, it crashes, and the surviving assimilated drones are now free from the collective (see Voyager episode Unity.) This Riker could be the one we saw in that TNG episode.