Browsers are open source and don't include any such blocking feature. ISP's can only block DNS which you bypass by changing DNS servers, a VPN will do this for you. Gab has their own servers, so it's not their web host. Most web hosts would also shut down the site entirely rather than restricting access, which is still rare action when it's about free speech.
Those captchas typically appear because bots and angry DDoS attackers will often use the same VPN you use, they use any VPN or proxy they can find.
Sometimes I have to go through a captcha for using a VPN and its from either the browser or the webhost.
Those captchas typically appear because bots and angry DDoS attackers will often use the same VPN you use, they use any VPN or proxy they can find.