You already know the answer. Exactly the same as in space, and it will be Handwavium'd with some non-sense about Thrusters maintaining positioning despite your Thrusters clearly not doing anything. You will be parked at 0m/s a couple km above a nice view, angled down enjoying the view, and think to yourself . . .
something feels off . . .
So, exactly how it currently works with the planets we can already land on?
Dispite what you may think, they do fire when you're within the gravity well of a landable planet, not to maintain position, but altitude.
You only need to enter the camera suite to see them working yourself. Turn off flight assist and they'll stop firing, followed by your eventual collision with the planet's surface.
Imagine the people that complain of too many buttons and complexity now being forced to constantly maintain enough momentum to keep from crashing while they fill their screenshot folders. It will not stand, man!
As other posts have stated, our ships are capable of operation on high-g planets, so there is zero need for us to maintain momentum just because there's now an atmosphere.
They aren't fixed wing aircraft which need momentum to remain airborne, they're spaceships easily capable of a 10g VTOL.