You Can Pass 421 HTTP Status to Googlebot to Opt-out of Crawling over HTTP/2
https://developers.google.comGoogle has updated its documentation on Googlebot add some info on their ability to crawl through HTTP/2 and how to opt-out of it temporary if your site is having issues when being crawled over HTTP/2.
To opt-out from crawling over HTTP/2, instruct the server that’s hosting your site to respond with a 421 HTTP status code when Googlebot attempts to crawl your site over HTTP/2. If that’s not feasible, you can send a message to the Googlebot team (however this solution is temporary).