Looks like OpenWRT 25.12.0 has a bug while trying to generate a custom image. Same issue while trying for two different routers.
'libubox20260213' does not exist, there's 'libubox20260313'
#OpenWRT @openwrt
github.com/openwrt/openwrt/issues/22412
I think the only thing holding it up is the package rebuild action.