Huawei
Disable Google Assistant from the Home Button auf Huawei
On Huawei phones running EMUI, the virtual home button doubles as a shortcut for the assistant app assigned in the system. A long press triggers whatever app is set as the default assist app, which is Google Assistant out of the box on most devices.
This behavior is managed separately from the Google app itself, so disabling Google Assistant inside the Google app will not remove the home button shortcut. The setting that controls it lives under the default apps section of the system settings.
To turn it off, open Settings ➔ Apps ➔ Default apps ➔ Assist app, then select the current assist app entry and choose None. Once no app is assigned, the long press on the home button no longer opens any assistant overlay.
Keep in mind that switching to None disables the shortcut entirely rather than swapping in another assistant. If you still want quick access to Google Assistant, leave the assist app set and instead adjust how it reacts inside the Google app settings, for example by turning off the always-on voice trigger.
This fix is useful if the overlay interrupts gestures or app switching. If the real annoyance is voice activation rather than the button, check the Google Assistant settings for the trigger detection option instead of removing the assist app assignment.