[shmizan]

There is no option for that in Kodi 18.
A workaround could be to use a proxy like nghttpx.

Or (not for the faint-hearted) you can comment out this line from xbmc/filesystem/CurlFile.cpp and recompile:
  g_curlInterface.easy_setopt(h, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_2_0);
Worked on my end...

my box doesn't have nghttpx, only nginx, and I have no idea how to use it (or even if it can be used to forward http2 as http1.1, or use it as both server and client).
seems like compiling from source might be easier 
thanks for the suggestions.