Use standard sysupgrade for major version upgrades. This is the default upgrade method mentioned in the release notes:
Download firmware images via the Firmware Selector or directly from our download servers:
An upgrade from OpenWrt 22.03 to OpenWrt 23.05 is supported in many cases with the help of the sysupgrade utility which will also attempt to preserve the configuration. A configuration backup is advised nonetheless when upgrading to OpenWrt 23.05. (see “Upgrading” below).