> I’ve spent almost two decades in digital-focused roles ... I've often thought about cybersecurity as something I'd like to specialise in

Because to me, cybersecurity reads like "more digital" than "strategy, user research", not less, I'm not sure if I know enough about the poster's motives to help.

But what I can suggest is that the late Ross Andersons' book Security Engineering is a great starting point to get into system security.

BTW, I have enormous respect for people who are transitioning between professional areas, and while it consumes energy it probably will be the source of more energy, best of success for everyone!