in boot mode:

% mount
<snip>
/dev/disk122 on /Volumes/TECHOBOOT (msdos, local, nodev, nosuid, noowners)

% ls -al /Volumes/TECHOBOOT
total 3735
drwxrwxrwx@ 1 bob         staff     2048 Feb  1 16:47 .
drwxr-xr-x  5 root        wheel      160 Feb  1 16:47 ..
drwxrwxrwx  1 bob         staff      512 Feb  1 16:47 .fseventsd
-rwxrwxrwx  1 bob         staff  1908736 Oct 13 08:37 CURRENT.UF2
-rwxrwxrwx  1 bob         staff      129 Oct 13 08:37 INDEX.HTM
-rwxrwxrwx  1 bob         staff      237 Oct 13 08:37 INFO_UF2.TXT


# nothing plugged in
% ioreg -p IOUSB > /tmp/a
# not boot mode
% ioreg -p IOUSB > /tmp/b
# bootmode
% ioreg -p IOUSB > /tmp/c


% diff /tmp/a /tmp/b
<snip>
>   | +-o TTGO_eink@14300000  <class AppleUSBDevice, id 0x100060fe4, registered, matched, active, busy 0 (18 ms), retain 14>

% diff /tmp/a /tmp/c
<snip>
>   | +-o T-Echo v1@14300000  <class AppleUSBDevice, id 0x100061000, registered, matched, active, busy 0 (25 ms), retain 16>

contents of: INFO_UF2.TXT

UF2 Bootloader 0.6.1-2-g1224915 lib/nrfx (v2.0.0) lib/tinyusb (0.10.1-293-gaf8e5a90) lib/uf2 (remotes/origin/configupdate-9-gadbb8c7)
Model: LilyGo T-Echo
Board-ID: nRF52840-TEcho-v1
SoftDevice: S140 version 6.1.1
Date: Oct 13 2021