Browserosaurus is an open-source (MIT license) browser prompter for macOS. It works by setting itself as the default browser; any clicked links in non-browser apps are now sent to Browserosaurus where it’ll present you with a menu of your installed browsers.
Switch Browser is a "Share Menu" extension for macOS which shows browser switcher anywhere where there's a webpage opened and Share menu is available (File -> Share in Crome for example or a dedicated button in Safari)