Is this Ra or a cover?
The instrumental is remade/replayed. Can't judge if it's Ra rerecorded as well or an impersonator. But it's definitley not the original version.
Warmly booming riffs
It does sound like Ra to my ears - and if it's not, it would be a huge insult to the god to hire someone to impersonate him to that level of detail and not just cut the man a check.
klezmer electro-thug beats
Yeah my best guess is the same - replayed instrumental, re-recorded Rakim, but it is the man himself. To be sure I haven't heard many attempts at "re-recording" rappers' vocals with soundalikes, as done for years to other genres of music by commercials, but my impression has been that with rap it's pretty hard to get somebody to actually like-for-like soundalike. But then...
On the one hand, you had people claiming Mr Fantastik (MF DOOM "Rapp Snitch Knishes") was Rodan from Monsta Island Czars. GTFOH, obvious fucking difference in vocal tone. Clearly I have some base level ability to tell when a rapper's voice is different.
On the other hand, I remember seeing Aries Spiers from MAD TV attempt a series of freestyles in various rappers' voices and being impressed. I don't know if he'd pass a blind test like this one, but if somebody on his level was able to imitate a rapper whose voice was as well known as Ra, would it fool me?
Anyway for his own sake I hope they paid him to get in the studio and kick it again. The man's still alive. No excuse.