These are my six¹ favorite² guitarists, listed in reverse order of when I first came upon and learned to love their music. Please recommend others.
Ben Monder³
Eivind Aarset³
Ava Mendoza⁴
Michael Brook³
Bill Frisell⁵
Robert Fripp
¹I likely forgot some.
²Ambientish and living
³Never seen live
⁴Used to see often in San Francisco before she left town
⁵Used to see often in New York City before I left town
A few that come to mind right off the top (not all exactly ambientish but all living, I think):
Dr Know (Bad Brains)
Mary Halvorson
Sumner McKane
Oren Ambarchi
Richard Pinhas
Sharif Sehnaoui
Robert Hampson
A few of my favs:
Johnny Guitar Watson
Leo Nocentelli
Jimmy Nolen
Andy Summers
George Harrison
John Lennon
Kenny Burrell
Jan Akkerman
Bas Krumperman
Eddy van Halen
I recommend Manuel Mota from Portugal, manuelmota.bandcamp.com