So to understand this I have to ask a few questions
You are running OS X 10.8.3 right?
B/c PT10.8.3 doesn’t exist, the highest that 10 went was 10.7.3 iirc.
I have nothing but love for Yosemite 10.10, it was a great release...I ran 10.6.x on it for the longest, great combo.
If you have browsers issues with your older OS X installs you could always buy an external drive and update that to something like Capitan
I actually just upgraded from Capitan to high Sierra, about 2 months ago..... the I found an awesome deal on a 2015 MBP and it came with Catalina so I am running that on my newer MBP.
That’s another option - a used MBP could be your option to stay away from upgrading
I am not running PT on any of these versions - just video stuff FCPX, I run PT on Windows with PTVersion 12.5.2 and Win10
Here is the OS compatibility chart to see which OS can run which version of software
https://avid.secure.force.com/pkb/ar...tibility-Chart