I belong to a few guitar forums. But quite honestly, none of them come even close to UU. Ukulele people are just plain nicer
There is a section of the UU Forum dedicated to guitar too.
Sopranos:Gibson Uke 1, Ukebrand Kumalae, Martin S-O, Northern JCD1, Risa Stick, Aloha plastic, Dixie banjolele, Macafferi Islander
Concerts: National Triolian, Koaloha Sceptre, Gold Tone banjolele, Kala SMHGCE-C, Gold Tone Banjo, vintage Harmony
Tenors: Godin MultiUke, Regal Wendell Hall Teeviola, Sonny Daze CBU, Oscar Schmidt 8-string A/E
Baritones: Bobby Henshaw
Concerts: Koaloha, Mainland mahogany
Sopranos: 1940s Gretsch, Kala Pineapple