The usual culprit should be the DNS filtering.
Either try different DNS providers to compare speeds, or you can use the system default DNS server.
Using the default DNS server usually solves all connectivity issues.
Switched to a Samsung from Huawei, now you noticed it, i can't unsee it.
l’m losing 80% dl speed with adguard (stable 3.6.3) on. Both phone have the same settings and everything's fine on the Huawei speedtest results
DNS doesn't do anythings tried off too.
I'm not really confident as i realize this issue is open since 8 months
I'm experiencing this issue on the latest 3.6.4 version, with my Mi Max 2 using Android 7.1. My net speed is 108-112mb, when AG is on, it drops to 30-50mb and doesn't go higher than 62mb according to speedtest.net. When it's off I get my full speed. First time I'm experiencing it and it's never happened on any previous version.