When recording (via pulseaudio), kwave eats 100% CPU.

Audacity, on the other hand, requires just 11% on my system.

You have a whole bunch of misfitting versions of framework components. Make
sure all the libkf5* packages have the same version (5.37.0-2)

So I'm using Bullseye now and kwave still takes 100% CPU.

Upgrading to Testing doesn't change things either.

Tested using pulseaudio backend.

Upstream bug (which this is likely to be):
https://bugs.kde.org/show_bug.cgi?id=445161

Versions of packages kwave depends on:
ii  kio                    5.78.0-5
ii  libasound2             1.2.4-1.1
ii  libaudiofile1          0.3.6-5
ii  libc6                  2.32-4
ii  libfftw3-double3       3.3.8-2
ii  libflac++6v5           1.3.3-2
ii  libflac8               1.3.3-2
ii  libgcc-s1              10.2.1-6
ii  libid3-3.8.3v5         3.8.3-16.3
ii  libkf5archive5         5.78.0-2
ii  libkf5completion5      5.78.0-3
ii  libkf5configcore5      5.78.0-4
ii  libkf5configwidgets5   5.78.0-2
ii  libkf5coreaddons5      5.78.0-4
ii  libkf5crash5           5.78.0-3
ii  libkf5dbusaddons5      5.78.0-2
ii  libkf5i18n5            5.78.0-2
ii  libkf5iconthemes5      5.78.0-2
ii  libkf5kiofilewidgets5  5.78.0-5
ii  libkf5service-bin      5.78.0-2
ii  libkf5service5         5.78.0-2
ii  libkf5textwidgets5     5.78.0-2
ii  libkf5widgetsaddons5   5.78.0-2
ii  libkf5xmlgui5          5.78.0-2
ii  libmad0                0.15.1b-10
ii  libogg0                1.3.4-0.1
ii  libopus0               1.3.1-0.1
ii  libpulse0              14.2-2
ii  libqt5core5a           5.15.2+dfsg-9
ii  libqt5gui5             5.15.2+dfsg-9
ii  libqt5multimedia5      5.15.2-3
ii  libqt5widgets5         5.15.2+dfsg-9
ii  libqt5xml5             5.15.2+dfsg-9
ii  libsamplerate0         0.2.1+ds0-1
ii  libstdc++6             11.2.0-10
ii  libvorbis0a            1.3.7-1
ii  libvorbisenc2          1.3.7-1