Google Chrome web USB serial socket permissions issues

Trying to use ESPHome Web to flash some firmware using Web Serial with Chromium, I got an immediate error when selecting a USB serial device: Failed to open serial port: FILE_ERROR_ACCESS_DENIED.

The issue had to do with ownership of the /dev/ttyUSB0 device file, which was group-owned by uucp on Arch Linux (Fedora might use dialout). Adding my user account to this group, running newgrp uucp and restarting Chromium from that shell session was enough to resolve the problem.

(The newgrp part is only needed the first time and avoids the need to completely log out and back in again)