The Senate shall have the sole Power to try all Impeachments. When sitting for that Purpose, they shall be on Oath or Affirmation. When the President of the United States is tried, the Chief Justice shall preside: And no Person shall be convicted without the Concurrence of two thirds of the Members present.
Judgment in Cases of Impeachment shall not extend further than to removal from Office, and disqualification to hold and enjoy any Office of honor, Trust or Profit under the United States: but the Party convicted shall nevertheless be liable and subject to Indictment, Trial, Judgment and Punishment, according to Law.
So to parse just a bit (even a non-lawyer like me can read this plain English) : "shall not extend further than to removal from Office". Since Trump is no longer holding public office, impeachment is not available. To disqualify Trump from future office is included only through the "and". It is not an either/or/whichever we choose option*. The text is clear. You cannot impeach someone is is not in office. Further, the Chief Justice is not presiding, making the entire affair extralegal.
I will not even get too deep into other issues with the impeachment. For instance the notion that Trump incited the riots when the justice department has charged some of the participants with "conspiracy" -- meaning they had advance plans for a crime, thus Trump could not have incited the riots. Nor the totally un-American notion of justice when the supposed "Judge" gets to vote on the conviction. I don't se a lot of justice there.
Trust me on this, the Democrats will rue the day they have taken this unprecedented act of political revenge. Biden participated in the unlawful spying on the Trump campaign with Obama. His dealings with Ukraine and China are still suspect. Can we go back and impeach Clinton again? No future politician will be safe. Jackson and Wilson and LBJ used the N-word with abandon. Several owned slaves. Are we going to go full Stalin and erase the history of any predecessor whose politics we do not like? Is the mere expression of one's First Amendment Rights a crime now?
This is a sad farce and politics at the most evil basic level. I spit on all concerned.
* Don't even start with the morally bankrupt Cabinet Officer from the Grant administration. He should have been allowed to resign and charged with the full might of the law for his malfeasance. First that guy was not the President, besides, precedent is not set in stone. I'm looking at you Dred Scott and Plessey vs. Fergusson. Do not waste my time on that specious argument.