dfu-util can be used to communicate with DFU (device firmware upgrade) enabled devices.

One example is the Leaflabs Maple mini boot loader.

Be sure to have the latest version installed from at least 2020 if you intend to use the Longan Nano which may not work correctly otherwise.

git clone https://git.code.sf.net/p/dfu-util/dfu-util dfu-util
cd dfu-util
sh autogen.sh
./configure --prefix=/usr/local
make -j 4
make install

$ dfu-util
dfu-util 0.9

Copyright 2005-2009 Weston Schmidt, Harald Welte and OpenMoko Inc.
Copyright 2010-2020 Tormod Volden and Stefan Schmidt
This program is Free Software and has ABSOLUTELY NO WARRANTY
Please report bugs to http://sourceforge.net/p/dfu-util/tickets/

You need to specify one of -D or -U
Usage: dfu-util [options] ...
  -h --help                     Print this help message
  -V --version                  Print the version number
  -v --verbose                  Print verbose debug statements
  -l --list                     List currently attached DFU capable devices
  -e --detach                   Detach currently attached DFU capable devices
  -E --detach-delay seconds     Time to wait before reopening a device after detach
  -d --device <vendor>:<product>[,<vendor_dfu>:<product_dfu>]
                                Specify Vendor/Product ID(s) of DFU device
  -p --path <bus-port. ... .port>       Specify path to DFU device
  -c --cfg <config_nr>          Specify the Configuration of DFU device
  -i --intf <intf_nr>           Specify the DFU Interface number
  -S --serial <serial_string>[,<serial_string_dfu>]
                                Specify Serial String of DFU device
  -a --alt <alt>                Specify the Altsetting of the DFU Interface
                                by name or by number
  -t --transfer-size <size>     Specify the number of bytes per USB Transfer
  -U --upload <file>            Read firmware from device into <file>
  -Z --upload-size <bytes>      Specify the expected upload size in bytes
  -D --download <file>          Write firmware from <file> into device
  -R --reset                    Issue USB Reset signalling once we're finished
  -s --dfuse-address <address>  ST DfuSe mode, specify target address for
                                raw file download or upload. Not applicable for
                                DfuSe file (.dfu) downloads
  -w --wait                     Wait for device to appear