OK, I installed SL and the computer runs quietly. The only issue I've found so far is that when I launch iTunes (most current version) I get an error message about some "Tea" plugin that can't be used. I have no idea where this plugin is so I can't get rid of it. It's not in ~/Library/Audio/Plug-ins. It must have come over when I did Migration Assistant from my MacBook. It sure is annoying.
However, Ubuntu was a pain in the backside to get installed (16.04). After installing the rEFind boot loader my 8 GB USB thumb drive simply wouldn't boot. I created one multiple times using unetbootin but each time it failed. I have no idea what I did differently to finally get it to boot; the thumb drive is initialized as FAT32 and GUID partition table. Anyway, I had to boot using the "Try Ubuntu without Installing" option (probably should have done this sooner) because booting from the "Install Ubuntu" failed with a boot error. Once booted into the "Try" option I was able to do the installation on the remaining 40 GB partition of my SSD. The track pad was sluggish and the pointer jumped all over the place (but works fine after the installation) so it was a bit challenging to get all the options. After reboot from install, there was no wifi and I had to find how to manually install the drivers (they were on the USB drive but not automatically installed). For those who may encounter this problem in the future, here's what I did:
Plug in the installer thumb drive. Two files needed located on the USB thumb drive:
pool/main/d/dkms/dkms_2.2.0.3-1.1ubuntu5_all.deb
pool/restricted/b/bcmwl/bcmwl-kernel-source_6.30.223.141+bdcom-0ubuntu2_amd64.deb
I copied these files to the root of the thumb drive and opened them in a window. I then opened terminal and typed this command:
sudo dpkg -i (dragged the bcmwl* file here) <ENTER>
sudo dpkg -i (dragged the dkms* file here) <ENTER>
And that was it; wifi worked great after that. There was an update to Ubuntu and after it installed I tried to reboot but the computer wouldn't shut down, so I had to do a hard shut off. After rebooting, the computer shuts down/restarts just fine. So, all seems good now.