Based on the definition from 538: Who Is Favored To Win The 2024 Presidential Election? | FiveThirtyEight.
The election is a landslide if the winning candidate receives at least 350 electoral votes. I will ignore faithless electors.
As of June 11th, the current 538 prediction is 33%:
Biden wins an Electoral College landslide: 23%
Trump wins an Electoral College landslide: 10%
Free mana here, No upsets is at 72% — upsets are required for either candidate to surpass 320 EVs
https://manifold.markets/ChinmayTheMathGuy/2024-presidential-election-result-m
Biden can get 350 with every 2020 state + Texas + NC + Florida or Alaska, whereas Trump needs every 2020 state + Virginia + New Mexico + Minnesota + Colorado. These maps are not impossible. If we naively extrapolate 2020 partisan bias of each state, one candidate needs a popular vote margin of about 10% for this to happen.