Problems running carla on UbuntuStudio 21.04

I don't know why carla is not working anymore on my system.

This is the error msg:

Carla 2.3.2 started, status:
  Python version: 3.9.5
  Qt version:     5.15.2
  PyQt version:   5.15.4
  Binary dir:     /usr/lib/carla
  Resources dir:  /usr/share/carla/resources
Traceback (most recent call last):
  File "/usr/share/carla/carla", line 46, in <module>
    host = initHost(initName, libPrefix, False, False, True)
  File "/usr/share/carla/carla_host.py", line 3227, in initHost
    gCarla.utils = CarlaUtils(utilsname)
  File "/usr/share/carla/carla_utils.py", line 333, in __init__
    self.lib.carla_cocoa_set_transient_window_for.argtypes = [c_uintptr, c_uintptr]
  File "/usr/lib/python3.9/ctypes/__init__.py", line 387, in __getattr__
    func = self.__getitem__(name)
  File "/usr/lib/python3.9/ctypes/__init__.py", line 392, in __getitem__
    func = self._FuncPtr((name_or_ordinal, self))
AttributeError: /usr/lib/carla/libcarla_utils.so: undefined symbol: carla_cocoa_set_transient_window_for

I already tried upgrading (Everything is up to date), searching for bugs in the carla GitHub (found nothing relevant) and reinstalling carla.

My system was in a borked state for some reason. I was able to get fix the problem by running:

sudo apt purge carla
sudo apt autoremove
sudo apt install carla

My guess is I updated /usr/share/carla/* a long time ago and forgot about it. When the system updated, some files got overwritten, but others not.

The Carla version in your question indicates that its origin is ubuntustudio backports PPA.

I would recommend to add this PPA and reinstall carla packages by

sudo add-apt-repository ppa:ubuntustudio-ppa/backports
sudo apt-get update

sudo apt-get install --reinstall $(dpkg -l | grep carla | grep ^ii | awk '{print $2}')