there were interesting investigation on nginx mailing list Re: nginxQuic: медленный ответ от сервера. <https://forum.nginx.org/read.php?21,294301,294466#msg-294466>
my translation: *What was found so far. Issue is located on Chrome/QUICHE side when EarlyData + HelloRetryRequest are bundled. If "EarlyData" was ignored by server, chrome is not sending another "ClientHello"in reply to "HelloRetryRequest"* Ilya
