Comment # 15 on bug 1190074 from Daniel Bauer

For your information:

The problem also exists on a fully updated OS 15.5.
The solution provided by Raphael Bertoche 2021-09-25 also works on OS 15.5:

adding the following line to /etc/profile.d/pulseaudio.sh:
export LADSPA_PATH=/usr/lib64/ladspa