I do this on all my PC's nearly every day, all use Mint 19.3 as i reverted back from 20.1, it had to much issues with Python 3 and LinuxCNC stuff.
Use at your own risk.
You’ll have to remove the lines that point to my old repo otherwise apt will have a bitch & moan.
Linuxcnc should be able to be updated from the official repos.
If only my brain chemistry could fixed as easily.
