Sorry I am not familiar with any free structured cycling training programs. I am sure many exist.
Like any training program, it should be specific to your goals.
A good program will address any specific weaknesses and incorperate some training dedicated towards injury prevention.
It should be structured with logical progression, rest/recovery and compliments your on the bike training.
I would recommend a periodised plan, just like TrainerRoad has structured their cycling program.
Typically in the strength world these phases are referred to as GPP (General Physical Preparedness), Hypertrophy, Strength and Power and or Strength Endurance pending which direction you wish to take with your training.
British Cycling has a few generic resources with advice that I believe is quite reasonable for the general public.
I have been looking for a way to give back to TrainerRoad as I am an avid podcast listener but I am fairly time crunched these days with a young family.
I have a bachelors degree in exercise science and practiced as an exercise physiologist focusing on musculo-skeletal injuries and strength training, but I have been out of the game for almost a decade now.
If you have any more specific questions I will try to answer them. Or if there is enough interest I might try do a write up on My opinions on strength training but I’m not a very polished writer and it would be pretty rough.
British Cycling Strength Exercise Recommendations
British Cycling - Winter Strength Training