I interpret my understanding of what you had written in a short summary:
"you come with skills (coding skills & IT management, i suppose) & ideas where you want to offer yourself to partner with a startup and grow with it - and you like to know how to make this happen"

There are many challenges that need to overcome before we even talk about offering ourselves to a startup:

1. Have you package yourself well so that you can market yourself easier and increase the chance to attract startups to take you in? You can't sell all your skills and ideas - your only saleable items are niche skills and valuable validated ideas.

2. Do you have personas for the startups so that you know who you are looking for?

3. It seems that you are very skillful and have many ideas, but these are professional's qualities and not an entrepreneur's qualities. To join as a team in the startup, you are acting as a partner rather than an employee. Have you conduct an evaluation or seek opinions from others on for entrepreneur's score or capability? In addition, you can't do everything from developing to maintain apps ... you probably will involve strategic planning to grow the startup and lead a small team when the startup grow - did you possess the necessary skills for theses?

4. It is essential to align your goals to your desires and how your involvement with startup affects your family and friends? This is critical to avoid making the wrong choices and developing unnecessary dissonance in the future.

If you have all the above, you know what to do next. Otherwise, contact me where I customise an advisory package based on what answers you have made.