$ gpg --lookup-key firstname.lastname@example.org
Toss in "-auto-key-locate=clear,wkd,nodefault" to force it to look there for the key even if it already has a key for that email address.
If one controls a domain, has HTTPS set up and uses PGP this is the easiest and most secure way to host a key (`gpg --list-keys --with-wkd $KEY` shows the hash value).
Enigmail, Mailpile, Mailvelope will automatically discover the key when composing an e-mail. ProtonMail is also working on integration of WKD with their web mail.