To move from OpenWrt v23.05.x or earlier to recent snapshots or the upcoming v24.10.0 release, you have to force-flash the unsigned v1.1.3 (or later) installer. If you want to keep your settings, keep a backup of your configuration as they are going to be lost when running the installer.
Either download https://github.com/dangowrt/owrt-ubi-installer/releases/download/v1.1.3/openwrt-mediatek-mt7622-linksys_e8450-ubi-initramfs-recovery-installer.itb and use that with the LuCI Firmware Upgrade UI. You will have to force-flash it and do not keep settings.
Alternatively you can also do this using SSH:
sysupgrade -n -F https://github.com/dangowrt/owrt-ubi-installer/releases/download/v1.1.3/openwrt-mediatek-mt7622-linksys_e8450-ubi-initramfs-recovery-installer.itb
After the installer has run, the device will boot into the recovery image and listen on 192.168.1.1. Now you can flash the snapshot sysupgrade.itb file.
If you restore your previous settings by replaying the configuration back file you need to make sure to also bump compat_version in order to be able to apply future sysupgrade:
uci set system.@system[0].compat_version='2.0'
uci commit system