(covers information from several alternate timelines)
The following is a list of unnamed Humans whose era is unknown.
Arab prince
One Arab prince coined the proverb "the enemy of my enemy is my friend", only to be betrayed and decapitated by his own subjects. Spock mentioned this in 2258 of the alternate reality when James T. Kirk suggested they work with Khan Noonien Singh, citing that saying. (Star Trek Into Darkness)
Archer's photograph
Captain Jonathan Archer placed a photograph of three Human men at the wall in his ready room aboard Enterprise NX-01. (ENT: "Regeneration")
Explorers
A group of Humans was known to have explored Earth's bodies of water in a primitive ship. (Star Trek: Enterprise opening credits)
Inheritor
This was one of the inheritors, the ancient Humans who received certain gifts from visiting Sky Spirits.
His image kept flashing in Chakotay's memory while visiting the Sky Spirits' homeworld in 2372. This was possible because memory of the event was one of the gifts. (VOY: "Tattoo")
Lavelle's grandfather
This Human was the grandfather of Sam Lavelle. He was Canadian.
In 2370, Sam felt, upon learning (erroneously) that William T. Riker was Canadian, that their shared heritage by virtue of his grandfather would give them a starting point for friendship. (TNG: "Lower Decks")
Little old lady from Leningrad
According to Pavel Chekov, a little old lady from Leningrad invented Scotch whisky. (TOS: "The Trouble with Tribbles")
The alternate reality version of Chekov made essentially the same claim, though only specifying that the lady was from Russia. (Star Trek Beyond)
Lover
This Human male crash landed on an unnamed Class M planet. He was nursed back to health by Anna. They fell in love, and died sometime before 2370. (TNG: "Liaisons")
McCoy's great-great-granddaddy
This Human lived in the American South and was rumored to have the finest garden in the area. He also had a recipe for weed spray that McCoy used against the swoopers on the planet Phylos in 2269. (TAS: "The Infinite Vulcan")
Picard family album photographs
The Picard family album contained a number of photographs of people, supposedly connected to the Picard family. (Star Trek Generations)
Riker's great-grandfather
According to William T. Riker, this man was once bitten by a rattlesnake, which died after "three days of intense pain". Riker related this to Deanna Troi in 2365 while suffering from the effects of the Surata IV microbe. (TNG: "Shades of Gray")
Sisko's great-great-grandfather
This Human had false teeth that he kept in a glass next to his rocking chair. In 2375, Benjamin Sisko mentioned him to Kasidy Yates as the couple imagined their life together. (DS9: "Penumbra")
Scott's grandmother
This Human was Montgomery Scott's grandmother. Scott likened the experimental transwarp drive that the USS Excelsior was equipped with to the equivalent of his grandmother being a wagon if she had wheels. (Star Trek III: The Search for Spock)
The alternate reality version of Scotty mentioned his grandmother to Jaylah. (Star Trek Beyond)
Troi family
Troi ancestor
A box of belongings owned by this ancestor of Ian Andrew Troi was sent to Deanna Troi in 2368 by her mother. (TNG: "The Outcast")
Subjects of photographs
These individuals were in photographs found in Deanna's ancestor's box. Most of their names were not written on the images, though some were. Deanna wondered which, if any, were related to her. When she showed the photos to William T. Riker, he pointed to one individual, saying they looked like her. (TNG: "The Outcast")