Recently I've been playing around with the Radxa ROCK 5B+. Turns out installing Gentoo on it is a rather involved process, especially if you want a bcachefs rootfs. For those of you wondering why on earth someone would want to do that: this post is not about the why, but about the how. I have my reasons.
The ROCK 5B+ supports loading U-Boot from its SPI NOR flash chip. However, that chip is empty when the board leaves the factory. It can also load U-Boot from a microSD card. So you could write Radxa OS to a microSD card, and continue from there, but I prefer using what I know. As I'm an OpenWrt developer, and I know that OpenWrt supports various Rockchip based boards, that's where I started. Checking the rockchip target in OpenWrt, I quickly learned it supports the ROCK 5B. Not the same board, but it's very similar. So let's build an OpenWrt image for the ROCK 5B, flash it to a microSD card, and see if it boots.
It does, but unfortunately I hit a bunch of problems along the way.