PikaOS maybe too “hobby oriented” to expect “sleep stability”, but I understand most/all bugs to be debian or kde upstream ones. Is gnome still much better at stability? Is there a distribution that fixed sleep problems for you? open vs closed nvidia drivers?
Are there motherboard manufacturers that suck less at linux?
Not sure if it is applicable, but wouldn’t it be an option to use the Fedora Workstation Live CD, mount your swap partition into the live system and send it to sleep via SystemD?
This should give you feedback with a fairly recent kernel and Gnome has (at least for me) been the desktop option with the least amount of bugs I encountered.