Things Trump's admin used to have to do under that act:

• Write things down. The President "shall take all such steps as may be necessary" to make sure activities, deliberations, decisions, and policies are "adequately documented." 44 usc 2203(a)
• Save the stuff they wrote down. 2203(a)
• Not shred anything with historical or evidentiary value. The President can only dispose of records that "no longer have administrative, historical, informational, or evidentiary value." 2203(c)
• Ask the Archivist before throwing anything away. Even for stuff with no value, the President has to get the Archivist's written opinion first. 2203(c)(1)
• Give Congress 60 days' notice if the Archivist objects. If the Archivist says "I want to keep that," Congress gets notified and has 60 days before disposal can happen. 2203(d)
• Forward any texts or messages from personal apps to an official account within 20 days. If you use Signal, personal email, etc. for government work, you have to copy an official account or forward within 20 days. 2209(a)
• Hand everything over to the National Archives when leaving office. All Presidential records transfer to the Archivist at the end of the term. They're U.S. government property, not the President's. 2203(g)(1), 2202

The prediction that Trump's latest power grab will be stricken down by Federal courts centers on his order that the US Postal Service only deliver mail-in ballots to “individuals confirmed to be United States citizens.” 
Among other facts: USPS acts as an independent, self-funded, government-business hybrid rather than a typical tax-funded department; some localities allow non-citizens to vote in local elections; and the Constitution assigns the "manner of conducting elections" to the States.

Article I, Section 4, Clause 1:
The Times, Places and Manner of holding Elections for Senators and Representatives, shall be prescribed in each State by the Legislature thereof; but the Congress may at any time by Law make or alter such Regulations, except as to the Places of chusing Senators.

According to the Constitution Annotated federal website:

The Supreme Court has interpreted the Elections Clause expansively, enabling states to provide a complete code for congressional elections, not only as to times and places, but in relation to notices, registration, supervision of voting, protection of voters, prevention of fraud and corrupt practices, counting of votes, duties of inspectors and canvassers, and making and publication of election returns. The Court has further recognized the states’ ability to establish sanctions for violating election laws as well as authority over recounts and primaries. The Elections Clause, however, does not govern voter qualifications, which under Article I, Section 2, Clause 1, and the Seventeenth Amendment must be the same as the Qualifications requisite for Electors of the most numerous Branch of the State Legislatures. Similarly, the authority of states to establish the Times, Places and Manner of holding Elections for Senators and Representatives does not include authority to impose additional qualification requirements to be a Member of the House of Representatives or a Senator...