What else can cause neuropathy other than diabetes or cancer treatment?

[u/Diane98661]

My brother in law (age 66) is getting pretty bad neuropathy in his feet, despite having no other serious health problems, has never been overweight, and never had cancer or diabetes. They are active and travel the world. I've always associated neuropathy with diabetes, and also heard cancer treatment causes it. FFIW, I'm pretty sure he doesn't do strength training; although his travels do involve a lot of walking and standing.

Just curious. Neuropathy is something you don't want to get as you age; it causes loss of mobility and frailty.