There are very good ideas here, but if I were a marine mammal without hands and I was made intelligent I would be aware of my physical limitations and I doubt very much that I would be happy among humans with fingers.
In my fictional universe, tech has advanced so far that any jackass can uplift any animal. So there are *lots* of poorly uplifted critters, and a fairly substantial ASPCA-like system to help them - which sometimes means putting them down. But cetaceans have been successfully uplifted several times; part of the process is genetic mods that allow them to easily interact with prosthetics that they can easily don and doff as they wish.
In one of my stories, a plot-unrelated bit happens when some humans on an ocean world see a pod of orca swim by, followed by a somewhat larger whale. One of the local humans explains to a confused off-world human that the larger whale is actually a robot; it follows the uplifted orca and contains all their stuff, including manipulators, drones, fusion reactors and fabricators (i.e. "replicators"). The orca are not dependent upon humans, but interact with them regularly. Many join starship crews.
Starships that have cetaceans onboard either have larger water-filled corridors or the cetaceans can go about in "wetsuits" and "fly" through the corridors via gravity manipulation. Bad science, but... meh. Space opera.
The gorilla thing would be even worse, everyone pretends I'm like a normal human and I'm smart enough to understand that they despise me.
Except the humans *don't* despise them. Uplifted gorillas in larger society are every bit as civilized as humans or anyone else. Nobody pretends they're human, any more than they pretend Thessi crewmates are human.
On the other hand, Neanderthals would have no problem integrating, in fact they have always been here.
Oddly, the Neanders integrate less well than the gorillas. In order to uplift gorillas (and cats, dogs, ravens, etc.), a *lot* of tinkering to their brains had to be done, and as a result their thinking is often almost human-standard. The Neanders, however, were left as baseline as they could be. (I presume that before Earth goes down, quite a number of DNA samples of Neanderthals are discovered and utilized). Neanders turn out to be rather baffling. Like us, but different in a lot of ways (including a "spiritual" existence that would put most shroomed-out shamans to shame). Enough so that they don't fit well. They're left to do their own thing.
Humans create these offshoots for shits and giggles as much as anything else. Because *of* *course* we would given the ability.