PPA addition taking too long

Question

I have a moderately new installation of Linux Mint 19.1. Since I installed it two months ago when I try to add a PPA by sudo add-apt-repository in terminal I get a black screen. At first I thought I broke apt, but then I accidentally walked away angry once. After almost 10 minutes the repository was finally added. I have since not been able to get a PPA to add in less time. They never fail, but always take a long time. I'm running a dell e6330. The system is using a SSD and nothing else really seems slow, and no other command takes that long. It isn't an internet problem because apt-get update works quickly.

Solution

I temporarily disabled IPv6 system-wide.

It seems to be a DNS routing issue. I was able to use the hotspot on my phone to troubleshoot and the problems went away.

sudo sysctl net.ipv6.conf.all.disable_ipv6=1

disables IPv6 until reboot.