How to change the default system font in Mac OS X

In the old editions of MAC OS , I was able to change the writing method of the OS by changing some of the files, but with the new edition of the MAC OS is now deferent , the old way is not efficient any more, is there any new way I can change writing method of the OS.
Specially to Ubuntu Arabic.

The issue seems complicated, or there is no solution

Have a look at this:

I didn’t try it myself (but I saw it on several machines) and I don’t know if it still works on the latest macOS.

Changing fonts names is not a solution; it is a circumvention of the system. It is the same manual method here

Changing the file name is not enough, of course. But the above repository should take care of that.

apple is apple : )