@SourMilk If you want a Openwrt 18.06 SDK version for your Opal, there's a copy of the gl-infra-builder here with instructions on how to compile a working clean Openwrt version:

git clone https://github.com/201821143044/gl-infra-builder.git && cd gl-infra-builder
python3 setup.py -c configs/config-siflower-18.x.yml && cd openwrt-18.06/siflower/openwrt-18.06
./scripts/gen_config.py target_siflower_gl-sft1200 luci
make V=s -j5

Immortalwrt built on the same sources is here:

Neither is true mainline Openwrt though.

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