The current Internet landscape is shaped by intermediate elements, known as middleboxes, which disrupt the end-to-end principle the Internet was originally designed around. In [5], the authors examine the HTTP/1.1 ~protocol and demonstrate that assessing the compliance of a remote implementation with respect to its RFC ~is challenging, as middleboxes on the network path can alter application-layer content. This paper builds on their work by focusing on HTTP/2, a more efficient yet more complex protocol that is known to be vulnerable to denial-of-service attacks. We create a suite of 156 tests, more than three times the number conducted on HTTP/1.1, and analyze 12 popular proxies as well as 3 cloud proxies. This work not only investigates the current landscape of proxy implementations with respect to RFCs, but also examines the evolution of compliance over time in local proxies. We show that while there is an improvement compared to previous results in HTTP/1.1, none of the proxies are yet fully compliant.