I might be confused …
You wrote … “i tried using Firefox and Chrome”
You tried “what” with Firefox and Chrome??
Running that URL? If yes, that should be executed at the command line, not in a browser.
There’s two commands being piped - basically, curl is downloading the public key, then that output is being redirected to a gpg file.
.
.
But for grins, here’s me running the first command (to show it is accessible)
.
calder@ren:~> curl -s https://brave-browser-apt-release.s3.brave.com/brave-core.asc
-----BEGIN PGP PUBLIC KEY BLOCK-----
mQINBFvFEDIBEADwix8cI/QMI36OjLMpL/2xX4D4JY
HZdqwja8xRRoQ7lnw2w+zv
GnyksvyL6ycEWVw06awzUq
.
+++++ snip a bunch of text
.
=F6zi
-----END PGP PUBLIC KEY BLOCK-----
calder@ren:~>