Hi.
- Flash a 22.03.6 factory image from OEM firmware. Don't set any setting except for password.
- Enter ssh and perform the kernel size change. Reboot.
- You can now flash anything. Flash the latest 23.05.2 factory or sysupgrade image. DO NOT keep settings while flashing.
- Flash again the same 23.05.2 image.
You will have 23.05.2 on both partitions. Enjoy.
There is no need to install Luci, it's already in any official stable images.