Using a Lenovo Chromebook with full hardware keyboard (and said emulation option selected) under ChromeOS version 97.0.4692.102 (Official Build) (64-bit), I am seeing that the hamburger menu (which brings up shortcut buttons at the bottom of the screen) may have some aberrante behavior. Using the shortcut buttons e.g. [Ctrl] [Esc] [Sym] etc. I would at least be able to select a control key in the popup, but unfortunately this does not work for Ctrl.
The Sym button works fine, as does the blank button (presumably enter raw command, as a line appears at the bottom of the screen which I can then Ctrl-V into) but tapping the Ctrl button seems to do nothing. I am able to bring up the Ctrl button by using the long-press menu and tapping or clicking CTRL+?, and I can reproduce this behavior in any terminal connection I use.
I've attached a screenshot of the aforementioned menu/buttons for clarity:
