This changes, not only over time, but also from region to region.

A close friend of mine travels to China often, and they use Mullvad because of my recommendation. Last year it worked great for them, but earlier this year they went back to China, and it really didn't work.

What I found most interesting is that they had different results in different places. Apparently, in the business areas of Shanghai and Beijing, were they had meetings and events, they could get Whatsapp and Slack messages; when they went back to the hotel, in a residential area where there were almost no offices or tourists, it didn't. In Chongqing even less stuff worked.

I was very skeptical of this when they told me, but they could replicate this consistently over a couple of weeks. It wasn't related to hotel Wifi (that's a different can of worms), this was on mobile data.

Everything worked when they switched to using https://letsvpn.world, at the recommendation of some chinese colleagues of them.

This was with a basic Mullvad install on iOS and Mac, they're not technical enough to harden their VPN connection further; may be they could've easily obfuscated it more and it would've worked.