nzb360 makes connections to web services with HTTP/1.1 even through proxies that support HTTP/2, as my nginx access log shows:

"GET /sabnzbd/api?mode=version&output=json&apikey=<redacted>&output=json HTTP/1.1" 200 20 "-" "-"

HTTP/2 has performance advantages which should improve speeds on remote connections especially.

Many nzb360 users run their services through a reverse proxy like nginx which has supported HTTP/2 for years.

SABmini on iOS, the closest competitor to nzb360 (for SABnzbd at least), does support HTTP/2 as shown below:

"GET /sabnzbd/api?apikey=<redacted>&ma_username=&ma_password=&output=json&mode=version HTTP/2.0" 200 40 "-" "SABmini/388 CFNetwork/976 Darwin/18.2.0"
It appears that nzb360 uses a very old version of okhttp for some services (I'm seeing user agents okhttp/2.7.5 for Sonarr/Radarr/SABnzbd and okhttp/3.9.1 for Deluge in my logs).

2.7.5 does not fully support HTTP/2 or TLS 1.3 among other things.
3.9.1 supports HTTP/2 (tested OK with Deluge) but not TLS 1.3.

Can it please be updated?