I can't imagine even SCOTUS would uphold a president pardoning themselves. Though the Constitution doesn't address that directly, it does address it indirectly...
The Constitution DOESN'T allow giving a pardon for cases of impeachment, which applies to all officers being impeached including the president. So if a president can't save themselves with a pardon for being impeached for a crime, I don't see why that same restriction wouldn't apply to facing criminal charges.
But it's a moot argument anyway since a president CAN get a pardon, with Congress' and their VP's assistance...
A president can resign, making their VP president and leaving the VP seat open. The new president can then pardon the criminal ex-president who then names the pardoned president as their VP, with congressional approval. Then the president resigns making the criminal VP, president again. Who turns around and appoints them VP, with congressional approval.
I don't see anyone ever pull a stunt like that but then I never thought I'd see a president send slates of fake electors from 7 states to Congress to flip an election they lost. So who knows?