LMMS 1.2.2 uses a ton of the cpu on Ubuntu 21.04 on raspberry pi 4

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Bug Summary

LMMS 1.2.2 uses a ton of the cpu on Ubuntu 21.04 64 bit on raspberry pi 4. I recently installed ubuntu 21.04 desktop on my raspberry pi and LMMS barely works. After configuring the audio server, I tried to play some songs that I had made on an old 32 bit version of lmms-1.1.3 on the same Pi, but running raspberry pi os 32 bit. The songs (being run on lmms 1.2.2) used up a ton of the cpu to where it was super glitchy. It was so bad that my mouse cursor barely worked. It seems like the newer LMMS is a downgrade and has poor function. Does anyone know what could be the problem?

Screenshot

When I took this, the song was barely playing and cutting out at times; I could barely stop the song and take the screenshot.

Affected LMMS versions

1.2.2

Reproduce LMMS 1.2.2 on Ubuntu 21.04 64-bit running on a Raspberry Pi 4, using one of the songs that showed the problem. Compare playback CPU usage and glitching with LMMS 1.1.3 on 32-bit Raspberry Pi OS, then identify and document the cause of the regression.