Thanks. Nothing obvious in the log unfortunately.
Can you try the following:
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Can you confirm whether the alternative method of using systemd.unit=emergency.target also works to boot to a command prompt, or does only recovery work ?
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Remove the options you added to cmdline.txt and try booting with your external USB devices removed - does that boot ?
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Try editing config.txt and add the following line:
dtoverlay=mmc
If you have a line that says:
dtoverlay=sdhost
then remove it. Does it boot now ?