Hi @nflaig - my apologies for my previous post on this, I misread what you’d been asking. I’ve since deleted it as it wasn’t much help.
In the meantime I did confirm this behaviour as a bug which appears to have been introduced in consul 1.9.0 (as you mentioned).
We’re tracking it here : ui: ui-content-path flag/config no longer works (1.9.0/.1) · Issue #9522 · hashicorp/consul · GitHub
And we’ve got a fix in the works which should hopefully make it into 1.9.2
My apologies for the earlier confusion, and thank you for reporting the issue!