EspoTek Labrador USB board on Raspberry Pi 4

EspoTek’s Labrador is an excellent single board, all-in-one USB oscilloscope / signal generator / power supply / logic analyzer / multimeter with a cross-platform Qt5-based GUI frontend. It is especially useful for use with Raspberry Pi-series computers. It works out of the box on RPi3 and earlier models, but unfortunately, as-shipped, RPi4 has a firmware bug which prevents Labrador from working.
To fix the unfortunate situation, you need to update the RPi4’s firmware to the latest version with a tool called rpi-eeprom.

1. Make sure your system is up-to-date, and install rpi-eeprom.
2. Change FIRMWARE_RELEASE_STATUS="critical" to "stable" in /etc/default/rpi-eeprom-update.
3. Run rpi-eeprom-update to check the status of the firmware. The result should look somewhat like this:
   

   BCM2711 detected
   Dedicated VL805 EEPROM detected
   BOOTLOADER: up-to-date
   CURRENT: to 3.9.2020 12.11.43 +0000 (1599135103)
    LATEST: to 3.9.2020 12.11.43 +0000 (1599135103)
    FW DIR: /lib/firmware/raspberrypi/bootloader/stable
   VL805: up-to-date
   CURRENT: 000138a1
    LATEST: 000138a1

   The current VL805 firmware version is the important one here, if it is older than 000138a1, you have to update the firmware.

4. The actual update happens when you then run rpi-eeprom-update with the -d switch (i.e. rpi-eeprom-update -d). The new firmware binaries are loaded during the following reboot. Ensure that the update was succesful by checking again with rpi-eeprom-update after rebooting.

For Arch Linux / Arch Linux ARM users:

I uploaded a Git version of Labrador GUI for Arch Linux to AUR. It supports 32-bit and 64-bit x86 architecture and several ARM versions (armv6h, armv7h, aarch64).