I manually set the "CPU Frequency Scaling Monitor" on my panel:
Lately, I've observed that the setting changes to "Ondemand", without my manually changing my previous manual selection of a fixed frequency!
This is not a single instance. It seems to be happening on a regular basis.
Anybody know why and how that is happening?
My experience is that the setting you change it to doesn't survive a reboot. I've never bothered to research it, but would be interested if anyone can provide insight.
Thank you,@mdd12. I was aware that it would not survive a reboot.
I am experiencing the change randomly while I am in the same session, after manually setting the frequency. 
I think some other process is also switching the frequencies and is doing so behind your back.
I don't know which one (there are several tools that can do that) but there is a lot info here:
https://wiki.archlinux.org/title/CPU_frequency_scaling
I've just created the following script to simplify the "learning curve" for the CPU frequency scaling. I hope that having set the mode and frequency using the cpupower utility, it will end the unexpected changes.
(edit #3: NOTE: I re-wrote the script to add a few more checks and balances to protect the user. 
)
(Sep 9 2024: In Addition to extensively modifying my script, I decided to move it from here and put it under its own topic for Tips & Tricks.