Multiple selection (shift-selection) seems to be broken for version 5.15.11 of PyQt5. It looks like the problem is in qtDisplay.py, where the keyboards modifiers (SHIFT) are directly compared with the Qt keyboard constants using == rather than using the & operator. I am not familiar with the details, but it works for me if I replace == with &.
Multiple selection (shift-selection) seems to be broken for version 5.15.11 of PyQt5. It looks like the problem is in qtDisplay.py, where the keyboards modifiers (SHIFT) are directly compared with the Qt keyboard constants using == rather than using the & operator. I am not familiar with the details, but it works for me if I replace == with &.