Depends on your distro. You need to set up all the requirements for hibernation (like “enough swap space to store current memory contents + whatever is left in swap” and zswap doesn’t count).
IIRC Fedora defaults to ZRAM instead of swap, so you probably need to set up a swap partition first. I don’t know if you need to disable ZRAM, but you probably need enough swap space on disk to store the contents uncompressed.
You’ll also need to modify the kernel parameters/initramfs configuration to add the resume parameters in the right spots, or the system will hibernate but not try to resume your session on boot.
Then there may be some selinux issues depending on if Fedora fixed them or not. I don’t think hibernation is supported by default on Fedora so you may need to tweak things like polkit files to get the permissions right.
I believe running the command sudo systemctl hibernate should manually induce hibernation. You can use it to test if your computer even has the ability to hibernate before figuring out what permission tweaks you need for KDE. Make sure you’ve saved your work before trying that, though, as not all systems will wake from hibernation without further troubleshooting.
You may also need to disable security settings like secure boot and/or kernel lockdown mode it hibernation might be refused.