You are not allowed to do this. @dos warned about related already. Librem 5 needs to be treated as home pet and not like some wild animal.
Please use: sudo systemctl poweroff before you start do destroy your Librem 5 microSD card slot.
EDIT: microSD cardreader not working - #13 by dos tells us: “please move the tray only when the phone is off, it isn’t really meant to be hotplugged”.