Unfortunately this is a big part of trusting your VPN provider. It’s shocking how bad the situation is, especially it seems on those marketed via Android apps. [1]
Well the VPN ecosystem has an enormous long tail - the paper you cite tested 283 (!) apps. It's unfortunate but somewhat expected that a significant number, especially the ones that haven't been around for long, would have issues.
I'm sure, given the size of that list, that they tested some of the biggest players on the VPN space. I think it'd be good to know which apps were tested and didn't show any issues, especially in light of Krack and the Android bug on wpa_supplicant.
Unfortunately this is a big part of trusting your VPN provider. It’s shocking how bad the situation is, especially it seems on those marketed via Android apps. [1]
[1] https://arstechnica.com/information-technology/2017/01/major...