@qwerty keyboard here are some links that will help you.
Find your Dram settings
https://forum.armbian.com/topic/29794-how-to-install-armbian-in-h618/#findComment-218660
Find boot.bin and extract dts.
https://forum.armbian.com/topic/29794-how-to-install-armbian-in-h618/#findComment-187672
Uboot defconfig. I have two x96q builds with ddr3.
https://github.com/NickAlilovic/build/blob/v20250306/patch/u-boot/u-boot-h616/151-add-x96-q-ddr3-defconfig.patch
Or
https://github.com/NickAlilovic/build/blob/v20250306/patch/u-boot/u-boot-h616/163-add-x96-q-ddr3-v5.1-defconfig.patch
You can edit the patch and enter the new values.
If you need to add a new line in the defconfig patch. At the bottom of the patch add your newline and put a "+" infront of it. Also, for x96q ddr3 increase @@ -0,0 +1,37 @@ to @@ -0,0 +1,38 @@ or for x96q ddr3 v5.1 @@ -0,0 +1,39 @@ to @@ -0,0 +1,40 @@.
Download and compile my build:
git clone https://github.com/NickAlilovic/build.git --branch v20250306
cd build
./compile.sh
choose "Do not change kernel configuration"
choose "Show CSC/WIP/EOS/TVB"
choose "I understand and agree"
choose "X96Q DDR3” or “X96Q DDR3 v5.1”
choose "edge"
rest is up to you.