ターミナルで、以下のように入力すると
brew install gcc
次のようなエラーが出る。
Searching for similarly named formulae...
Error: No similarly named formulae found.
Error: No available formula or cask with the name "gcc".
==> 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.
この通りにbranchを切り替えると解決する
https://github.com/Homebrew/discussions/discussions/708