no wifi hardware installed on Mojave update
I edited the /etc/sysctl.conf file. There are three settings adjusting socket buffers to improve broadband performance. I doubled the numbers there and it fixed the networking issues.
   There was a constant stream of error messages saying sockets were unable to allocate buffer memory. Apparently, there is a process crashing somewhere and not releasing it’s socket buffers. I don’t know which one is doing it because it is hard to track down due to the sluggishness.