Looking for new music with guitar in those 2 areas. I know the big names so I am looking for guys/gals who are under the radar.
I don’t know what new classical music is being written for guitar, but as far as jazz goes, definitely check out Julian Lage and Bill Frisell.
Also Russell Malone. He works in more of a traditional jazz style than Frisell or Lage. Well worth a listen.
Pasquale Grasso is also fantastic. Stylistically, I’d say he’s kind of the heir to Joe Pass.
Have you tried Bossa Nova?
João Gilberto
If by “new” you mean “new to me” rather than music being written and performed today, my absolute favorite jazz guitar player is Grant Green. He recorded a bunch of great stuff in the '60s.
Check out Lenny Breau. The Swinging on a Seven String album is particularly fun, he jazzes up some country standards.
He’s not exactly under the radar, but for my money Tuck Andress has the most unique style and attack. And his guitar doesn’t sound so much like a “jazz guitar”, if you know what I’m talking about. I really hate that sound.
I mean new to me
I’ve been listening to Eric Gales, Also Tommy Emmanuel.
Shubh Saran
Have you heard the 2014 “Guitarias” album of the SDMB’s very own Le_Ministre_de_l_au-dela? (Boy, that username did not translate well into the new Discord nomenclature format.)
Solo guitar and voice, really beautiful. (And some Doper names thanked in the liner notes! 
)
Nicola Hall was a superb classical guitarist. She released several albums in the 90s. Largely they consist of transcriptions of classical works for other instruments. She recorded 3 superb albums while still in her 20s. My understanding was that she then suffered hand problems that caused her to retire. However on Spotify there is also a recording released in 2012 but I don’t know when it was recorded.
Thanks for that, Chef Guy.
Don’t know if he is still active – haven’t heard anything of him for a couple of years – but you might look into Anton Del Forno. He is/was performing and composing for classical guitar for many years. He toured world-wide but was based in New Jersey where he played many local concerts.
I met him around 1970 (just after his Carnegie Hall concert at the age of 17) when he was staying with a neighbor in Malibu. My house was the party house and Anton would sit and play for us … really incredible, he would let us put an ear on his guitar while he used all four fingers of his right hand and his left little finger to do the tremolo thing … you’d swear you were listening to to a violin.
For a more flamenco-influenced classical sound, there is Ottmar Liebert:
Also more of a fusion of flamenco/rock/jazz sound, try Al Di Meola with Paco de Lucia or either artist alone:
How about Bireli Lagrene ?
He plays a pretty mean bass too.
And then there is Acoustic Alchemy, also very orchestral playing with Spanish influence:
Jason Vieaux is quite established (Grammy winner) so he may not fit in your “under the radar” category but he is my favorite classical player.
Stephanie Jones is my favorite new classical guitarist. She is based in Germany and has just released a new CD. I had hoped to see her on her U.S. tour last year but COVID killed it.
For jazz, lesser-known players I like are Corey Christiansen and Sheryl Bailey (but they are not particularly new).
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His playing is captivating, although honestly I think people are more impressed by his astonishing technique than artistic expression. He is a great solo player, but Joe Pass was a totally different type of player.
I love Tuck Andress but I’m not so much into Tuck & Patti. I wish he would record more solo material.
I wasn’t either until I saw them in a small venue concert a couple of years ago. They’ve really got a great chemistry, especially for a married couple who has to tour for a living. Just watching him play and hearing them riff off each other is a real treat.
Strongest recommendation so far. Very unique craftsman with his fingerpicking and right hand independence. I’m always discovering something new when listening to him.- sometimes it sounds like there’s more than one guitar going on.
Would that include icons Joe Pass and Jim Hall?
For classical, Christopher Parkening is a go-to for me, with his often Spanish-inflected leanings.
Here, doing J.S. Bach’s Prelude From Cello Suite No. 1
I’m guessing you’re familiar with Andres Segovia, so I won’t link.