Hi Morgan,
My L ankle has always gone over easily too and I’ve always been very cautious on trails with lots of exposed roots and rocky scrabbly downhills. My best recommendation from personal experience is single-leg strengtheners, esp. those that improve balance. Targeted strength training is the first line of defence against injury. I can make a personal plug for Chamonix Mountain Fit as a fantastic first step in this regard. At the gym, single-leg straight leg deadlifts on a balance disc have been amazing for me — they strengthen all the little intrinsic muscles in the foot and ankle. My other strong recommendation if you’re not already experienced with strength training: start slowly and light and proceed cautiously. Two to three months of CMF (2x per week) would be a great intro/transition phase before moving to more intense exercises, esp. using dumbbells or kettlebells.
Have you consulted with a physio or coach? A structured, tailored plan would allow you to progress more quickly and with less possibility of overdoing it or injuring yourself. Since there’s a structural difference between your two feet, I would urge you to see a physio in any regard. I am now at 52 dealing with a host of issues related to postural and structural imbalances that were not addressed when I was younger. Prevention is the best cure!
Jane