Are you looking for a shaped result? That'll show "whatever bandwidth
is left on the sector" without Libre, and around the customer's paid-for
target with Libre (hopefully!).
One thing Preseem does well is that their onboarding process includes
"leave it in monitoring-only mode" for a week, gathering data before you
pull the switch (although most ISPs I've talked to just pull the switch...)
It's quite enlightening to see a before/after, even with only FQ_CODEL
as the shaper.
We could probably do something similar with a "monitor only" mode that
doesn't enable any queues (is there a TC equivalent to "dummy" on
FreeBSD?).