I did sleep studies, medicines (including modafinil which worked but had scary sides), natural supplements (which helped but tended to result in lesser quality sleep).

In the end I needed to make sleep my number one priority and I focused on it for several months.

I slowly built up what worked for me, but likely won't work for you. A lot of being in bed at 10 staring at a dark ceiling for 3+ hours. Getting into meditation (in the am, not evening), exercising but never after noon and not eating after 6. Alcohol in any amount won't prevent my sleep but will vastly deteriorate the quality.

It took tons of trial and error to do what medical professionals couldn't help with. My conclusion is sleep is complicated and highly individual. You need to identify the things that wreck your sleep and pick them off with serious attention to them.