no wifi hardware installed on Mojave update After Mojave install I get a "No WiFi hardware installed" when trying to connect the wife. Computer response is so slow it's almost useless. Same results on iMac 27" Retina Display Mid 2015 and Mac mini Late 2012. Tried NVRAM and SMC resets to no avail. iMac worked fine when I reverted back to High Sierra but backup for mini is on the WiFi network.
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.