I had troubles with SD card (USB mass storage as well) in the near past which still are not solved.
https://forum.khadas.com/t/tf-card-not-detected-on-vim3-ubuntu-server-focal-linux-4-9-arm64-emmc-v0-9-20200530/8368/18
I know it could seem a nonsense, but in case you don’t have HDMI connected please try to connect a monitor to the board and check if SD works.
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