Fountain members Y-Haplogroup's list with direct links to join:

E1b1a - M2
891 members
https://www.familytreedna.com/groups/e-1b-1a

R-M269
R _R1b ALL Subclades
https://www.familytreedna.com/groups/r-1b

I-M223 Y-Haplogroup
https://www.familytreedna.com/groups/m223-y-clan

J-M172
J M172 - J2 Y-DNA
https://www.familytreedna.com/groups/j2-m172

G-M201
G-Uncategorized&Root Project
https://www.familytreedna.com/groups/g-uncategorized

E-M35
E-M35_Project
https://www.familytreedna.com/groups/e-3b

and/or

E-M35 etc Scotland
https://www.familytreedna.com/groups/e-1b-e-3b-e-m35-in-scotland
(requires you fill in form to join)

R-Z156
R _R1b ALL Subclades
https://www.familytreedna.com/groups/r-1b

R-Z156
R U106 (R1b-U106)
https://www.familytreedna.com/groups/u106

R-Z156
R-U106xL48WTY
https://www.familytreedna.com/groups/r-u10-6x-l48wty
(requires you fill in form to join)

R-FGC11134
R FGC11134 & Subclad
https://www.familytreedna.com/groups/r-fgc11134

R-DF49
R-DF49 and Subclades
https://www.familytreedna.com/groups/r-df49

R-M458
R1a-L260
https://www.familytreedna.com/groups/r-1a-l260

I-M253
I1 Z17954 [xDF29] YDNA Project
https://www.familytreedna.com/groups/i1-z131y-dna

I-M253
I1-L300 & Subclades
https://www.familytreedna.com/groups/i1-l300-subclades

I-M253
I-L1248
https://www.familytreedna.com/groups/i-l1248

I-Z63
I1>Z58+ and I1>Z63+
https://www.familytreedna.com/groups/2121

I-Z63
I1-PR683+/Y2245+
https://www.familytreedna.com/groups/i1-pr683y2245