Most cases of guinea - chicken hybrids are because a chicken rooster breeds a guinea hen. The actual breeding act for guineas is enough different from chickens that it is unlikely that the guinea cock will successfully breed your chickens.
You stopped your search too short which will show that chickens, turkeys, guinea fowl, peafowl, etc. are all from the same Family - Phasianidae.
Just because a "featured snippet from the web" which gives no source for its claim says something does not mean that you should believe it. By...
Turkeys, guinea fowl, chickens are members of the Family - Phasianidae. Guinea Fowl are no more closely related to turkeys than they are to chickens.
You are correct that for proper development, guinea keets should be started on a high protein turkey or game bird starter. Raising guinea...
If at all possible try to rehome it to someone that has guineas.
Possibly.
I feed my guineas pelleted feed.
If at all possible, try to rehome it to someone who already has guineas.
It is most likely that it just lost its mate to a predator and got lost while trying to escape.