It’s difficult to find knowledgeable TRT doctors anywhere, you’ll find doctors doing all sorts of drastically different things, only a few get things right.
SHBG is not something easily manipulated, the liver does what it wants. You can become obese and insulin resistant which will lower it, or you can throw excess testosterone to suppress it. Your pituitary gland is lazy, it should be increasing LH to get more testosterone out of your testilcles.
When SHBG is high, LH is a better indication of T status. As far as microdosing TRT to decrease SHBG, the opposite is true for high SHBG men. Excess testosterone is what lowers SHBG, microdosing is best for men with low SHBG or those sensitive to estrogen.
The boron is a long shot, you might as well consume Jack’s magic beans. High SHBG is a mix of genetics and cutting, starvation diets to look leaner. This increases SHBG and lowers testosterone at the same time and before you know it FT is very low.
If you were somehow able to decrease SHBG 63->20, your TT will drop lower than half of what it is now and you would still be stuck with low testosterone. So fixing SHBG naturally is a colossal waste of time because at the end of the day testosterone is still low.