There are a number of topics in the Support Desk that indicate that installing/upgrading to MediaWiki 1.35.x can render a wiki unusable. See Index.php displayed with wrong characters on Project:Support desk (mediawiki.org) and Has MW 1.35 changed when/how the HTTP header, Content-Length, are used? on Project:Support desk (mediawiki.org) as two examples, there are more.
This is being tracked as ⚓ T235554 MediaWiki::outputResponsePayload seemingly causes net::ERR_HTTP2_PROTOCOL_ERROR 200 and compression issues in 1.35 (wikimedia.org) and a few others.
Should the Release Notes page include a warning about these problems so that anyone upgrading is aware of the problem?