I've accidentally created the most divinely comfortable chub rub shorts / knickers EVER by cutting off a pair of old M&S cotton leggings to the knee.
Honestly, try it. They don't fray (you can fold up to make a cuff if you really want to), and the fact that they are cotton rather than polyamide is just joyous. You don't even need pants underneath, in fact they are better without.
Augment the effect by applying anti-perspirant on pant line and inner thighs.
🌞