Thank you @jack and @Alvin! I was initially referring to the 4-pin header on the board, the one close to the USB C-connector, but I guess using UART3 from u-boot as console works too.
However, I tried putting in the overlays=
in my uEnv.txt file, but I on reboot I get this:
reading /dtbs/4.19.193-24-rockchip-g526c758e05e0/rockchip/rk3568-radxa-e25.dtb
144983 bytes read in 51 ms (2.7 MiB/s)
** Unable to read file /dtbs/4.19.193-24-rockchip-g526c758e05e0/rockchip/overlay/rk3568-fiq-debugger-uart3m0.dtbo **
** Unable to read file /dtbs/4.19.193-24-rockchip-g526c758e05e0/rockchip/overlay/rk3568-disable-npu.dtbo **
… and it seems my /boot/dtbs/4.19.193-24-rockchip-g526c758e05e0/rockchip/overlay/
directory doesn’t contain these files. I’m using radxa-e25-ubuntu-focal-server-arm64-20220801-0210-gpt.img.xz
currently.