OpenWrt 19.07 on devices with small kernel partition

I think the way is to update existing firmware with unlocked u-boot-env partition, then change magic number from userspace with fw_setenv and then upgrade it to new firmware with modified kernel space.

It is been a while, I noticed that the problem was fixed in regular tree of OpenWrt, I've just easily compiled the image for AP147_10 with version 19.07.6. But, today I've discovered that the ImageBuilder version is still have this bug:

Image Name:   MIPS OpenWrt Linux-4.14.221
Created:      Wed Mar 10 18:14:26 2021
Image Type:   MIPS Linux Kernel Image (lzma compressed)
Data Size:    1589436 Bytes = 1552.18 KiB = 1.52 MiB
Load Address: 80060000
Entry Point:  80060000

The directory build_dir/target-mips_24kc_musl//linux-ar71xx_generic/ of openwrt-imagebuilder-19.07.7-ar71xx-generic.Linux-x86_64 does not have any custom image for this profile... I guess it must have?

so... could maintainers fix that?