I almost never agree with Reason and do not agree with textualism. I do agree with if / then logic. If one accepts textualism; then one must reject Trump's claim of sweeping immunity. In fact, one must reject any form of Presidential immunity.
I personally think there is an implied Presidential qualified immunity, further supported by precedents.
That would only apply to official acts as President in carrying out official duties while in office. I do not think election tampering on his own behalf qualifies as an official act.