In sleep mode the fan of the PC don’t stop now ; this happens wit xfce or kde-plasma rev 6.7.5 desktop
My PC is a Dell Inspiron type , 4 years old , and it’s the same with another linux distro on this computer - Mx - but not with Windows 11 OS ; I suspect then the linux kernel 6.18.53.1-lts
Any idea / advise , please ?
I use coolercontrol : https://aur.archlinux.org/packages/coolercontrol
Mine was racing on an old Dell XPS I had once-this resolved it for me.
I am unsure if it will help you or not but it might?
Also, if it is an older PC when was the last time you dusted it out and renewed the thermal paste on it?
Might benefit from that to 
EDIT: 4 years is not THAT old but I change my paste every 2-3 just to be sure.
EDIT 2: This may be of some help if you are unfamiliar with the process : otherwise a friend/family/local tech is yer friend
Try
cat /sys/power/mem_sleep
echo deep | sudo tee /sys/power/mem_sleep
Then suspend. If the fan stops, you’ve found the cause (s2idle vs deep) and the kernel is off the hook.
A couple of days ago there was a kernel update, maybe it will help.
Or try a non-lts kernel.
Oups a new info : after update in mode sleep, fan stop but it restart 3 mn after automatically !!! and screen also start and request password !!! I fail to understand …
Try updating your BIOS and any available firmware updates for your Serial Number/Service Tag.
I am unsure how to do this in Linux, not ever having to do it it myself and never looking it up.
After that just test it to see if the issue remains or not.