After a rocky start, the ASU server is now working properly (the build storage was full). At this point, ASU upgrades have been tested and all tests ran seamlessly for tested devices and profiles. If you encounter issues with ASU upgrades, please report them on the respective client threads:
Rockchip target
The rockchip target has no builds in this release, they crashed during phase1 and so nothing is available; just stay on -rc3 for now (or jump to -snapshot, if you need something recent - https://openwrt.org/releases/25.12/changelog-25.12.0-rc4#targetrockchip_6_changes).
LuCI ASU
The LuCI Attended Sysupgrade front-page notifications received a complete overhaul, removing that front-page toggle among other things. Comment on the appropriate link above if you see weird behavior.