Is it acceptable to ask or present a recommendation letter from a professor who left the university?
Yes he can give you a reference.

But he can’t say he is still at X university , it has to be clear he has moved on just in case they try to contact him.

People move all the time...

Some universities still receive reference requests for professors who are no longer available (death, no contact etc) and organize another professor or the Dean to write a reference to help the student.