Honestly?
I think he would have pushed hard to keep the original May 1st date. There would have been more emphasis on getting Americans out, and there probably would have been more US equipment destroyed and left than there was. (as distinct from the US furnished ANA equipment) We blew a ton of stuff in place when we unassed Syria. So the months leading up to the end date would have seemed more hectic, with top down orders to "Get out, Now!" and scorched earth equipment. But more people would have left. I think there would have been some American Civilians that refused to leave (NGOs, American University folks, stuff like that) because Orange Man Bad! and he said to.
May 2nd would have been right at the start of fighting season and the Taliban probably would have moved out and progressed at a pretty similar pace, only Kabul would have fell months after we left, instead of days.
The groups of vets and contractors would have had all summer to sneak people across the Turkmenistan or Uzbekistan borders, so more of the Commando's may have survived. By roughly now we'd be in a similar spot with Taliban spinning up their killings and solidifying control.
Trump would have been impeached over it.
I think the only way 2021 ends with the Original Afghan government still in control is if we left ISR and some limited Air Support in country to support the Afghan Commandos, and Trump pretty clearly wasn't going to do that. Trump was too invested in "ending the wars in the mideast" to sell a support force to maintain Afghan stability.