The dissent would disagree.
https://www.supremecourt.gov/opinions/23pdf/23-939_e2pg.pdf (page 68)
I'm not going to go through the dissent line by line to see what I agree with and what I don't. However, it's obvious that doing anything drastic like declaring himself a dictator or assassinating a rival falls outside of the president's duties and would not be legally protected. Neither, for that matter, would hoarding classified documents or arranging a fraudulent scheme to stay in office after losing an election. There was already an obvious understanding that Trump was not being prosecuted for simply doing his job. This ruling simply invents a redundant legal controversy and creates a new hoop for the prosecution to jump through. It's a cowardly ruling that comes entirely down to their fear of actually having to make a definitive ruling on whether or not Trump can be prosecuted rather than any real constitutional concerns, and it's giving Trump exactly the delay he wanted, but I don't think it actually changes anything about what the president is or isn't allowed to do. In that respect, I partially agree with Action80, although it's interesting that he apparently interprets Trump and the Court wasting everyone's time to be a good thing.
Not neccessarily. Trump's team has, because of this ruling, already filed a motion to overturn his hush money verdict. The reason being that, up until this ruling (despite what Action says), everyone thought the President's actions were usable as evidence in a criminal trial. But now, apparnetly, his tweets while president, can NOT be used as evidence of a crime. Which was used in the hush money trial and thus could invalidate the verdic.
The issue we have is what is defining as a president's duty? Aside from the costitution, there's no real line. A vague line, but no firm one. Like, the president is tasked with protecting the country from threats both foreign and domestic, right? So what if the president feels his political rival is a threat to the nation? Trump has said he'd be a dictator on Day 1. If that's not a domestic threat to the repubic, I don't know what is. Why would stopping such a threat be outside of his official duties as president?
As for the scheme to stay in office: Since he was president when he did most of that, any evidence of a crime is basically inadmissable in court. That speech he had? Inadmissable if you can reasonable claim its part of his official duty as president. (communicating with the people?) Challening the votes and stopping it could also be cosidered his official act to ensure a fair and balanced election. And any evidence of a crime could easily be marked as acts of the president, which is literally what they ruled. Like when he met with his temporary attorney general and told him to put pressure on certain people. That's no longer usable evidence in court. THAT, I think, is the most damaging.
And now a judge has to figure out what is or isn't official acts and have that challenged and possibly to to SCOTUS for each and every single one. Just the January 6th case could take years to go to trial. And the docuemnts case... who knows.
But remember: He owns one of the two major parties.
He appointed 3 of the 9 justices.
Even if SCOTUS just kicked the can back down the line, they kicked it with a list of restrictions.