undefined symbol: PaAlsa_EnableRealtimeScheduling prevents mixx application from opening

Question

In this machine, we have Ubuntu 20.04 (i suppose). After a few hardware configurations (some cables) (i don't really know about to explain), the mixxx software doesn't open.

So, it shows up in the Activity bar but then it doesn't open.
I tried to kill the process with killall command.
I tried to restart the machine.
I tried to reinstall the Mixxx software from the ubuntu software center, and from the console with the apt-get command.

Any advice would be useful.

I don't have physical access to the machine right now but I can manage it from my house with AnyDesk software.

(P.S.: I am not familiar with ubuntu software almost at all, so please give explanation answers :) )

Edit:

epalxeis@epalxeis-To-be-filled-by-O-E-M:~$ mixxx
mixxx: symbol lookup error: mixxx: undefined symbol: PaAlsa_EnableRealtimeScheduling
epalxeis@epalxeis-To-be-filled-by-O-E-M:~$ 

I tried to install it from source (link). Same error.

epalxeis@epalxeis-To-be-filled-by-O-E-M:~/Desktop/mixxx-2.3/build$ cmake --build .
Scanning dependencies of target benchmark
[  0%] Building CXX object lib/benchmark/src/CMakeFiles/benchmark.dir/benchmark.cc.o
[  0%] Building CXX object lib/benchmark/src/CMakeFiles/benchmark.dir/benchmark_api_internal.cc.o
[  0%] Building CXX object lib/benchmark/src/CMakeFiles/benchmark.dir/benchmark_name.cc.o
[  0%] Building CXX object lib/benchmark/src/CMakeFiles/benchmark.dir/benchmark_register.cc.o
[  1%] Building CXX object lib/benchmark/src/CMakeFiles/benchmark.dir/benchmark_runner.cc.o
[  1%] Building CXX object lib/benchmark/src/CMakeFiles/benchmark.dir/colorprint.cc.o
[  1%] Building CXX object lib/benchmark/src/CMakeFiles/benchmark.dir/commandlineflags.cc.o
[  1%] Building CXX object lib/benchmark/src/CMakeFiles/benchmark.dir/complexity.cc.o
[  1%] Building CXX object lib/benchmark/src/CMakeFiles/benchmark.dir/console_reporter.cc.o
[  1%] Building CXX object lib/benchmark/src/CMakeFiles/benchmark.dir/counter.cc.o
[  1%] Building CXX object lib/benchmark/src/CMakeFiles/benchmark.dir/csv_reporter.cc.o
[  1%] Building CXX object lib/benchmark/src/CMakeFiles/benchmark.dir/json_reporter.cc.o
[  2%] Building CXX object lib/benchmark/src/CMakeFiles/benchmark.dir/reporter.cc.o
[  2%] Building CXX object lib/benchmark/src/CMakeFiles/benchmark.dir/sleep.cc.o
[  2%] Building CXX object lib/benchmark/src/CMakeFiles/benchmark.dir/statistics.cc.o
[  2%] Building CXX object lib/benchmark/src/CMakeFiles/benchmark.dir/string_util.cc.o
[  2%] Building CXX object lib/benchmark/src/CMakeFiles/benchmark.dir/sysinfo.cc.o
...
...
...
[ 99%] Linking CXX executable mixxx-test
/usr/bin/ld: libmixxx-lib.a(sounddeviceportaudio.cpp.o): in function `SoundDevicePortAudio::open(bool, int)':
/home/epalxeis/Desktop/mixxx-2.3/src/soundio/sounddeviceportaudio.cpp:340: undefined reference to `PaAlsa_EnableRealtimeScheduling'
collect2: error: ld returned 1 exit status
make[2]: *** [CMakeFiles/mixxx-test.dir/build.make:1659: mixxx-test] Error 1
make[1]: *** [CMakeFiles/Makefile2:1155: CMakeFiles/mixxx-test.dir/all] Error 2
make: *** [Makefile:163: all] Error 2

Answer 1

I have just comment(//) lines339 and 340 of file /home/epalxeis/Desktop/mixxx-2.3/src/soundio/sounddeviceportaudio.cpp changing this:

#ifdef __LINUX__
    if (m_deviceTypeId == paALSA) {
        qInfo() << "Enabling ALSA real-time scheduling";
        PaAlsa_EnableRealtimeScheduling(pStream, 1);
    }
#endif

to this:

#ifdef __LINUX__
    if (m_deviceTypeId == paALSA) {
    //    qInfo() << "Enabling ALSA real-time scheduling";
    //    PaAlsa_EnableRealtimeScheduling(pStream, 1);
    }
#endif

and then I ran:

sudo cmake --build build --target install --parallel `nproc`

and now mixxx opens.

I don't know what side effects this custom install may do, so feel free to comment.