Please allow the tio snap to use classic confinement.
tio is a serial TTY I/O application that connects to serial devices in eg. /dev/serial/by-id/*
To do so classic confinement is required because snapcraft only supports allowing access to explicitly defined serial devices. This type of application is supposed to connect to any serial device.
In the future, it would be great if snapcraft could allow access to any serial type device via the serial-port plug.