AltGr on Italian keyboard mapped to Left Control+AltGr

I can replicate this issue using the tester:
https://guacamole.apache.org/pub/tests/guac/keyboard-test.html

Input method: English (UK) with Italian keyboard.
Tested both on external USB keyboard and built-in laptop (Lenove ThinkPad) keyboard.

Browser: Version 118.0.5993.118 (Official Build) (64-bit)
OS: WIndows 10 Enterprise

If I press AltGr once I get:

guacamole	keydown	0xffe3	Left control
guacamole	keyup	0xffe3	Left control
guacamole	keydown	0xfe03	AltGr
guacamole	keyup	0xfe03	AltGr

If I keep it pressed and then released it is even weirder because I get

guacamole	keydown	0xffe3	Left control
guacamole	keyup	0xffe3	Left control
guacamole	keydown	0xfe03	AltGr
guacamole	keydown	0xffe3	Left control
guacamole	keyup	0xffe3	Left control
guacamole	keyup	0xfe03	AltGr

This interferes (on a Ubuntu remote server) with using AltGr as the Alternate characters key, it just does not work. The workaround that I am using at the moment is that I have changed the "Alternate Characters key" in the keyboard settings on the server to the "Menu key".