It seems to basically mirror Republican policy.

No, here is the relevant line from Governor Gavin Newsom.

“The Supreme Court can now correct course and end the costly delays from lawsuits that have plagued our efforts to clear encampments and deliver services to those in need.”

They plan on giving services to homeless people. This would presumably include shelter.

You’re acting as though the Democrats are not willing participants in making homelessness illegal, but then linking to an amicus brief where they’re begging the Supreme Court to let them do just that.

This Supreme Court decision will most likely remove the Eighth Amendment protection that homeless encampments currently have. While that will remove their current legal standing, by which I mean how they are currently defended in courts, it will not impact the legality of homeless encampments one way or another. Laws will have to be passed and in some cases laws may already be on the books, that will determine the legality of homeless encampments. The Supreme Court cannot write, pass, or sign legislation to make homelessness illegal. As long as Biden is president, homelessness will at least be a state issue as apposed to a federal issue. If Trump becomes president homelessness will be a federal issue.

If they thought there was any threat from the legislature to actually ban Trump from running, the ruling would have been more expansive.

With the current Republican House of Representatives, there is little chance of Congress barring Trump from office. Under a Democrat controlled Congress they could bar Trump from holding office, but that would of course be too little too late. That is neither here or there though. The point of that example was to demonstrate that the Supreme Court can only determine who has authority in any given case, whether that be the federal government or individual state governments.

To be clear, the difference between Democrats and Republicans on this issue of homeless encampments, is that Democrats want their blue states to be able to help homeless people the way they see fit, which I agree is not the best way to do this, while Republicans want to make homelessness illegal at the federal level. If he is elected, Trump is going to decide what happens to homeless people in California, not Gavin Newsom. Trump is a fascist, so when he says "tent cities" on "large parcels of inexpensive land" he means death camps. So even though Democrats are approaching this with supposedly the best interests of homeless people in mind, it's not going to matter because Trump, if elected, will pull the rug out from under them. edit: typos