I have been running Motul DOT 5.1 synthetic brake fluid for several years in my BMWs at flush time.
https://www.amazon.com/Motul-100950-.../dp/B07KYWH2W8
Less propensity for water absorption, higher boiling point and longer service life, IMHO.
This fluid in conjunction with SS/teflon brake line upgrades has given me a much firmer pedal feel and braking action.
To each their own.
Mike