Here's something I kinda threw together that gets EDK2 usable on an OrangePi 5 max. https://github.com/RAMJAC-digital/edk2-rk3588/tree/main
It's an archlinux PKGBUILD that applies a couple patches for the device drivers and HDMI. This can probably be repurposed to build on any linux distro. Obviously flash your firmware with caution, but it's been booting from SPI to NVME without any issue for a while now.
If there is more interest in this, I can fully flesh this out.
I think that my problem is similar to this [1]. Have tried more than one USB to serial adaptor with the same result, the adaptors work fine on other boards.
The board boots Armbian fine with nothing connected to the serial port.
[1] https://github.com/Joshua-Riek/ubuntu-rockchip/issues/1073
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