There aren't any Armbian builds for 5.15 is what I said. And it would be a lot of work to make that happen. Why do you want 5.15? How do you know that would work, when 6.12 doesn't?

You can just download rock-3a edge(6.18+) images (not vendor 6.1) and change the device tree entry (sdcard/boot/armbianenv.txt) to point to "rockchip/rk3566-radxa-cm3-io.dtb" . This seems to boot fine with majority of features working.

no , i ment , currently armbin version is 6.xx right ///// i want armbian 5.15 version to build to my stb

@Werner Sorry for disturbing. I found that my board is actually 3 gb variant. Removed the heat sink. It is actually 3gb variant. The problem was hardware. We can close this topic.

There are no Armbian builds that old, in fact Amlogic TV boxes weren't incorporated into Armbian until later Linux kernels. What you must have been using would most likely have been a fork of Armbian. What you are asking for isnt possible in the way you are asking. You essentially want Armbian ported to the 5.15 Linux kernels, which is a huge project. You would be better served but spending a month or so figuring out why current kernels don't work for you and fixing that.