IDE 1.8.13 fails to upload to Esplora but Uno and Nano work fine

It's the same old 'can't open device "/dev/ttyACM0": Permission denied' problem, but just for Esplora.

On Linux the current IDE (1.8.13) fails to upload to an Esplora, though Nanos and Unos have no problem. Works fine on Mac OS with Arduino 1.8.12 and 1.8.11.

I'm in the 'dialout' group and the OS sees the Esplora.
Permissions on /dev/ttyACM0 are 666

Any ideas?


Background Info

Ubuntu 20.10
Arduino 1.8.13

Board: Arduino Esplora
Port: /dev/ttyACM0
Programmer: AVRISP mkII

Get Board info reports:
BN Arduino Esplora
VID 2341
PID 803C
SN (null)

Here's what happens when I try to upload to an Esplora

Forcing reset using 1200bps open/close on port /dev/ttyACM0
PORTS {/dev/ttyACM0, } / {} => {}
PORTS {} / {/dev/ttyACM0, } => {/dev/ttyACM0, }
Found upload port: /dev/ttyACM0
/snap/arduino/50/hardware/tools/avr/bin/avrdude -C/snap/arduino/50/hardware/tools/avr/etc/avrdude.conf -v -patmega32u4 -cavr109 -P/dev/ttyACM0 -b57600 -D -Uflash:w:/tmp/arduino_build_59446/Dimmer_Buttons.ino.hex:i

avrdude: Version 6.3-20190619
Copyright (c) 2000-2005 Brian Dean,
Copyright (c) 2007-2014 Joerg Wunsch

System wide configuration file is "/snap/arduino/50/hardware/tools/avr/etc/avrdude.conf"
User configuration file is "/home/bill/snap/arduino/50/.avrduderc"
User configuration file does not exist or is not a regular file, skipping

Using Port : /dev/ttyACM0
Using Programmer : avr109
Overriding Baud Rate : 57600
avrdude: ser_open(): can't open device "/dev/ttyACM0": Permission denied

Here's what dmesg says

[27407.444435] usb 3-2: new full-speed USB device number 11 using xhci_hcd
[27407.599588] usb 3-2: New USB device found, idVendor=2341, idProduct=803c, bcdDevice= 1.00
[27407.599593] usb 3-2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[27407.599595] usb 3-2: Product: Arduino Esplora
[27407.599598] usb 3-2: Manufacturer: Arduino LLC
[27407.601551] cdc_acm 3-2:1.0: ttyACM0: USB ACM device

$ ll /dev/ttyACM0
crw-rw-rw-+ 1 root dialout 166, 0 Dec 7 19:14 /dev/ttyACM0
$ id
uid=1000(bill) gid=1000(bill) groups=1000(bill),4(adm),20(dialout) (and 7 others)

Have you added the port to the dialout? Please check this article

See the bottom of my initial post. The /dev/ttyACM0 file is owned by' root', group is 'dialout'. Immediately below that you can see the results of running 'id' which indicates that I'm a member of 'dialout'.

One additional piece of info:

I installed Arduino 1.8.13 on a Raspberry Pi 4 running Buster and the Esplora works fine there.