starting mid November 2020, Googlebot will support crawling over HTTP/2 for select sites.
It is the next major version of HTTP and Google has added support for it through Googlebot. HTTP is used for transferring data by the internet. Google has a pet name for it, h2.
Read more on HTTP/2
Googlebot will decide whether or not crawl a website using h2 standards. If you want to opt out of h2 crawling for your website,
You can do that by instructing the server to respond with a 421 HTTP status code when Googlebot attempts to crawl your site over h2.
h2 has some real upgrade in client and server-side. Google is currently preparing to adjust itself to a new standard and getting ready to be available when indexing really asks for h2 standards in crawling. If you website is eligible for h2 crawling, you will get a message about the same in the search console. Make sure that you serve HTTPS if you want to make use of h2 crawling.
And the question want to ask after reading all this, shall I switch to h2 crawling and get a ranking boost ? Google says, NO.