How do I disable special character suggestions while typing?

Likely depends upon which Mac and which keyboard you're using.

On my 2021 MacBook Pro 14", running macOS Monterey 12.3.1, with TouchForce keyboard, System Preferences, Keyboard includes the option to turn Key Repeat off.

When set to Off, it entirely removes all pop-up special character suggestions.

It should only pop up if you hold down the key for a long time. Does yours pop up immediately?

The delay is tied to the "Delay until repeat" setting in Keyboard System Preferences. You could set that to a longer delay.

Daniel Derome wrote:

Hi.

Is there any other way to remove the special characters popup than through the terminal?

Thanks.

Try playing with the repeat and delay settings in system prefs / keyboard / keyboard

Daniel Derome wrote:

Hi.

Is there any other way to remove the special characters popup than through the terminal?

Thanks.

Old issue, new issue, what changed?

(Control–Command–Space bar) can be used to pop up that “Emoji & Symbols” / ”Character Viewer” window from any app.

You can try a safeboot to sort anomalies—

—SafeBoot How to use safe mode on your Mac - Apple Support

Takes a bit longer to get to the login screen, does a quick disk repair before it fully boots up, and certain system caches get cleared and rebuilt, including dynamic loader cache, etc.

Login and test. Reboot as normal and test. Caches get rebuilt automatically.

Uninstall all third party apps that are Cleaners/Optimizers/VPN/Anti-Virus

all known to cause issues on the macOS