Warm reboots: other images
What a warm reboot is and what it doesn't reset is on Warm reboots.
Install kexec-tools from your distro (kexec-tools on Debian, Ubuntu, Arch and Fedora). Then either run the script that ships with ps5-linux-tools:
cd ps5-linux-tools
sudo ./ps5-linux-warm-reboot.sh
Or do what it does by hand. It reads the kernel, initrd and command line from the boot partition, so whatever you have just updated there is what boots next:
sudo kexec -l /boot/efi/bzImage --initrd=/boot/efi/initrd.img --append="$(cat /boot/efi/cmdline.txt)"
sudo systemctl kexec -i
On a system without systemd, replace the second line with sudo kexec -e. On a Bazzite-based image the boot partition is at /efi, not /boot/efi.
Confirmed on original PS5s and Slims with Ubuntu, Arch and PS5 Bazzite Deck. The console's LED stays white; the PS5 OS is never started.
A kernel that doesn't boot costs you a full cycle through the PS5 OS, the jailbreak and the loader. Load it with kexec first: if it fails, power off and the old kernel is still on the boot partition.