systemctl --type=device 
UNIT                                                                                         LOAD   ACTIVE SUB     DESCRIPTION                                             
sys-devices-platform-soc-20201000.serial-tty-ttyAMA0-hci0.device                             loaded active plugged /sys/devices/platform/soc/20201000.serial/tty/ttyAMA0/hc
sys-devices-platform-soc-20201000.serial-tty-ttyAMA0.device                                  loaded active plugged /sys/devices/platform/soc/20201000.serial/tty/ttyAMA0   
sys-devices-platform-soc-20202000.mmc-mmc_host-mmc0-mmc0:aaaa-block-mmcblk0-mmcblk0p1.device loaded active plugged /sys/devices/platform/soc/20202000.mmc/mmc_host/mmc0/mmc
sys-devices-platform-soc-20202000.mmc-mmc_host-mmc0-mmc0:aaaa-block-mmcblk0-mmcblk0p2.device loaded active plugged /sys/devices/platform/soc/20202000.mmc/mmc_host/mmc0/mmc
sys-devices-platform-soc-20202000.mmc-mmc_host-mmc0-mmc0:aaaa-block-mmcblk0-mmcblk0p3.device loaded active plugged /sys/devices/platform/soc/20202000.mmc/mmc_host/mmc0/mmc
sys-devices-platform-soc-20202000.mmc-mmc_host-mmc0-mmc0:aaaa-block-mmcblk0-mmcblk0p4.device loaded active plugged /sys/devices/platform/soc/20202000.mmc/mmc_host/mmc0/mmc
sys-devices-platform-soc-20202000.mmc-mmc_host-mmc0-mmc0:aaaa-block-mmcblk0.device           loaded active plugged /sys/devices/platform/soc/20202000.mmc/mmc_host/mmc0/mmc
sys-devices-platform-soc-20300000.mmc-mmc_host-mmc1-mmc1:0001-mmc1:0001:1-net-wlan0.device   loaded active plugged /sys/devices/platform/soc/20300000.mmc/mmc_host/mmc1/mmc
sys-devices-platform-soc-soc:audio-sound-card0.device                                        loaded active plugged /sys/devices/platform/soc/soc:audio/sound/card0         
sys-devices-virtual-block-ram0.device                                                        loaded active plugged /sys/devices/virtual/block/ram0                         
sys-devices-virtual-block-ram1.device                                                        loaded active plugged /sys/devices/virtual/block/ram1                         
sys-devices-virtual-block-ram10.device                                                       loaded active plugged /sys/devices/virtual/block/ram10                        
sys-devices-virtual-block-ram11.device                                                       loaded active plugged /sys/devices/virtual/block/ram11                        
sys-devices-virtual-block-ram12.device                                                       loaded active plugged /sys/devices/virtual/block/ram12                        
sys-devices-virtual-block-ram13.device                                                       loaded active plugged /sys/devices/virtual/block/ram13                        
sys-devices-virtual-block-ram14.device                                                       loaded active plugged /sys/devices/virtual/block/ram14                        
sys-devices-virtual-block-ram15.device                                                       loaded active plugged /sys/devices/virtual/block/ram15                        
sys-devices-virtual-block-ram2.device                                                        loaded active plugged /sys/devices/virtual/block/ram2                         
sys-devices-virtual-block-ram3.device                                                        loaded active plugged /sys/devices/virtual/block/ram3                         
sys-devices-virtual-block-ram4.device                                                        loaded active plugged /sys/devices/virtual/block/ram4                         
sys-devices-virtual-block-ram5.device                                                        loaded active plugged /sys/devices/virtual/block/ram5                         
sys-devices-virtual-block-ram6.device                                                        loaded active plugged /sys/devices/virtual/block/ram6                         
sys-devices-virtual-block-ram7.device                                                        loaded active plugged /sys/devices/virtual/block/ram7                         
sys-devices-virtual-block-ram8.device                                                        loaded active plugged /sys/devices/virtual/block/ram8                         
sys-devices-virtual-block-ram9.device                                                        loaded active plugged /sys/devices/virtual/block/ram9                         
sys-devices-virtual-misc-rfkill.device                                                       loaded active plugged /sys/devices/virtual/misc/rfkill                        
sys-devices-virtual-tty-ttyprintk.device                                                     loaded active plugged /sys/devices/virtual/tty/ttyprintk                      
sys-module-configfs.device                                                                   loaded active plugged /sys/module/configfs                                    
sys-subsystem-bluetooth-devices-hci0.device                                                  loaded active plugged /sys/subsystem/bluetooth/devices/hci0                   
sys-subsystem-net-devices-wlan0.device                                                       loaded active plugged /sys/subsystem/net/devices/wlan0                        

LOAD   = Reflects whether the unit definition was properly loaded.
ACTIVE = The high-level unit activation state, i.e. generalization of SUB.
SUB    = The low-level unit activation state, values depend on unit type.

30 loaded units listed. Pass --all to see loaded but inactive units, too.
To show all installed unit files use 'systemctl list-unit-files'.