Even with HPKP, many libs/apps behave like Firefox/Chrome in this respect:
"""
Firefox and Chrome disable pin validation for pinned hosts whose validated certificate chain terminates at a user-defined trust anchor (rather than a built-in trust anchor). This means that for users who imported custom root certificates all pinning violations are ignored.
""" Firefox and Chrome disable pin validation for pinned hosts whose validated certificate chain terminates at a user-defined trust anchor (rather than a built-in trust anchor). This means that for users who imported custom root certificates all pinning violations are ignored.
"""
https://developer.mozilla.org/en-US/docs/Web/HTTP/Public_Key...