I'd be ok with Hawkgirl or Vixen as John's love interest tbh, whether it be in s2 of this series or just down the road in the greater DCU sandbox. Whatsherface who plays Hawkgirl was pretty good in Superman and would have fit the mold of what imo was missing in the casting news for this series: a young attractive love interest. Ofc a young hot brehetta would be even better from an optics standpoint.
Remember, in the animated show John was jugglin both at one point and each had a fun contrasting style to his more humble beginnings, blue collar persona: Vixen as the ultra rich and famous model/socialite and Hawkgirl as this hotheaded alien warmonger from an advanced society.