For years Libre Office 5 to 6 to 7 has made the fan in my laptop speed up to annoying levels. I just found that if I disabled OpenCL in the advanced options dialog (alt)F12, a bunch of small CPU activity across multiple cores went away and the fan is silent finally.
This is under Windows 7, an old Lenovo IdeaPad Y580, but the fan problem occurs in my HP zBook15 as well.
This is a Christmas miracle, since this laptop has been on 24/7 since 2013, and I love it dearly. The horror of having to buy a new laptop and install the hundred programs is a source of anxiety, so I hated that Libre Office would get the fan going, since I am sure any thermal cycling would reduce whatever life is left on this machine.
No more opening a document, work on it for a few minutes and then closing it so I don’t hear the fan. It looks like a great 2022. Sorry if you feel this is silly, but I searched and searched over the years, not finding anything. It was an article about turning off the Java Runtime that got me to the “Advanced” menu, looking one level below came to “Open CL” choice, and that one little checkbox that solved a 5-year problem.