I guess EV certs can help. This one just uses Let's Encrypt but GitHub have their company name in the URL bar for official sites.

WHOIS

I don't have time for that every time I encounter a new domain.

This functionality could be automated with a browser extension, or even as a built-in feature where there isn't an EV cert.

Then your whois provider gets to see all the domains you are visiting in real-time.

Good point. Even though your ISP/DNS provider can see this too (including HTTPS connections) it's prudent to limit data leakage as much as possible. Perhaps the lookup could require a single click (only needed when you are unsure of the owner).

If you're using the default whois that comes with OS X you're out of luck.

$ whois github.audio

whois: audio.whois-servers.net: nodename nor servname

provided, or not known

This is a handy alias to have: whois='whois -h whois.geektools.com'

Probably the same on Windows 98 or XP.