You’re good! Give it a reboot and see if this worked. 
It worked! Yay! As my high school senior would say, you’re savage. 
Do you have any recommendations for the sound?
Awesome! Believe it or not, the sound is a much easier beast to handle. The reason is that the main system runs on Pulse Sound, which still has ties (and is based on) the primary system called ALSA. There’s a great chance that your audio is just muted from there.
Install the following app from your software store:
Then run it and raise the volume bars to see which one engages your sound. 
Bad news…I installed QasMixer and it wasn’t working so I was playing with the settings and it crashed. I decided to do a reboot. Now the touchpad doesn’t work again. I took a screenshot of the mixer - 2 of the devices don’t work, oss and shm.
I did tell you I’m running Mint from a thumb drive, didn’t I? With persistence.
Yes, you did! Which could be a very good reason as to why the touchpad DKMS didn’t stick. It’s a Kernel Module and apparently it doesn’t do well with module additions that go beyond the persistent area.
Hi Vasilieos, So does that mean I won’t be able to run Mint on my MacBookPro with a thumb drive, and have a functioning touchpad? Also sound?
What persistence means is that you will be able to save your files on your thumb drive, your browser history, your settings etc. All of that normally resides within your /home/username folder and it’s a differently mounted area.
System files however, like Kernel Modules may apply on the RAM-Drive that the OS creates upon boot, but when you restart, it gets wiped. So, essentially, unless you actually install it on a USB thumb drive, the live version kind of resets each time.
That makes sense. Thank you for your explanation. So I could either run that code every time I boot up, or get a USB-C wired mouse. At least for now.
Do you have any other ideas for the sound problem?
What a second…I just re-read your explanation. Can I install that code for the touchpad on the thumb drive so that it runs on every boot? Or maybe make the thumb drive like a dual boot? It has 128GB on it.
You could use a thumb drive for that, provided that your Mac will load through it. Yes. However, in order to avoid changing your MacBook’s boot loader, I would recommend installing the boot loader directly onto the boot drive itself. Which means - when you go for the installation - to select manual partitioning (at the screen where it asks you where to install Ubuntu). I can help you with that if you like.
Also, keep in mind, the installation thumb drive has to be a different one, not the same with the Live Image. So, you can flash a 8-16GB USB stick and use your bigger one for the installation. 
In the installed version, any changes and additions you do to the system/kernel/modules, they all stick!
Ok, that’s good news. So just to clarify. I want to make a USB thumb drive into a bootable Linux drive to use with my MacBook. This will preserve the Mac but give me the option to use the MacBook as a Linux machine by booting through the USB thumb drive. All the settings and tweeks we do in order to get the touchpad working, and the sound, will be preserved on the thumb drive. This is different from a flashed thumb drive. Do I have it right?
If yes, I would like help with that please. 
Yes! Once you install Ubuntu on an actual medium, all system update restrictions are automatically lifted. The flashed USB will be different than the installation one. The one you install Linux into will act as a normal drive.
Thus, I would recommend flashing a 8-16GB USB and use your 128GB as the installation target. This will mean that - at some point - you will need to have both of them plugged in.
Once you flash the smaller USB, boot from it but don’t plug in the bigger one just yet. You can do that the moment the smaller (flashed) USB reaches the graphic interface. Then you can plug the big USB and it will immediately be recognized and become an available medium for installation.
When you are ready to begin, I recommend having your phone available and logged in the forums so that you can post some pictures of the process. Then, I can guide you step by step.
Wonderful! I will get the thumb drives together and set some time aside this week. I didn’t expect to get a response from you today - hope you’re having a relaxing Sunday.
Until our movement grows bigger, I tend to be “on call” basically 7 days a week. When I’m not around the forums, it means I’m preparing something else for us. 
Best of wishes for an awesome day!
Hi Vasileios,
I spoke with you some time ago about creating a bootable thumb drive for my Macbook Pro. Well, I’m ready to do it. I have the 2 USB thumb drives ready to go, so when you have the time, let me know. Appreciate your help very much. No rush! I can imagine you are swamped. 