brew install [email protected] Updating Homebrew... To restore the stashed changes to /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core, run: cd /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core && git stash pop ==> Auto-updated Homebrew! Updated 1 tap (homebrew/core). ==> Updated Formulae Updated 1 formula.
==> Searching for similarly named formulae... Error: No similarly named formulae found. Error: No available formula or cask with the name "[email protected]". ==> Searching for a previously deleted formula (in the last month)... Error: No previously deleted formula found. ==> Searching taps on GitHub... Error: No formulae found in taps.
Looks like 5.9 is not support for home brew you will need the dmg
https://download.qt.io/archive/qt/5.9/5.9.7/
If you want to build and install yourself here are the steps. This is what I needed to do
https://doc.qt.io/archives/qt-5.9/osx-building.html