What are the Halachik issues with donating sperm in a non-Jewish community?
No, a Jewish man cannot be a sperm donor.
Based on tshuvos from Reb Moshe (Igrot Moshe, Even Ha'Ezer 1:71 & 4:32.5) we can say
Niuff byad is an issur which only married couples who undergo IVF can get around, but single guys in a clinic can't.
The assumption is that the sperm will go to a nonjew, so there is no kiyum of pru urvu to dissipate the issur of hotzaas zera livatala.
Since you can't guarantee that a Jewish woman won't end up impregnated with said sperm, you run into a problem of siblings from the same father possibly marrying each other, which is arayos and makes mamzeirim.