On macOS, it's the "intuitive" command + option + i , which I can never remember (and then you still have to click on the stupid security tab, which is hidden if you don't have enough horizontal space on the dev tool frame)
It is much worse than the previously convenient click-on-lock-icon -> view certificate. Even on windows, F12 is usually a Fn key, so I have to select Fn+F12 which I never knew till the GP pointed it out to me.