[D] Physicist-turned-ML-engineer looking to get into ML research. What's worth working on and where can I contribute most?

After years of focus on building products, I'm carving out time to do independent research again and trying to find the right direction. I have stayed reasonably up-to-date regarding major developments of the past years (reading books, papers, etc). but I definitely don't have a full understanding of today's research landscape. Could really use the help of you experts:-) A bit about myself: PhD in string theory/theoretical physics (Oxford), then quant finance, then built and sold an ML startup to a large company where I now manage the engineering team.