Framework / questions for CTO mentors

Hello! I've been retained by a couple of venture funds and some startups, to act as a technical Expert In Residence (CTO mentor/coach) - about 20 very early stage companies in many different verticals.

For technical founders here and CTOs, what are the kind of questions you would have for someone as a technical advisor? If you basically had someone else paying for an experienced but part-time technical person, what would you like most help with?

Often founders have exceptional expertise in a specific domain, but lack the broad know-how to build a profitable business. You might be an expert on say graph algorithms for drug discovery, but know nothing about building a platform, or acquiring users. Would that type of know-how be helpful?

Ideally I'm looking to design a framework for multiple engagements with very different companies. I've started a few ventures myself, but have no formal technical education, so there's a bit of impostor syndrome here for sure. I don't think trying to advise CTOs or founders on their specific domains would be helpful, but at the same time I want to avoid giving generic advice that is a waste of time.

Is there a very specific area of CTO expertise that would be useful to multiple companies across different verticals? eg security, hiring practices, remote team building, metrics, process scaling?
Or would you prefer someone to dig in and help you brain storm to develop an algorithm together? Or figuring out how to find a business model for a technical breakthrough?

What are hard technical lessons you've learned in your first venture?

Hard questions in the abstract, but the situation has many variables. Appreciate any ideas to make this a bit more systematic!