Yes you could put a portable basketball hoop in the ground if you want too.
You would either remove the basketball hoop base and just bury the pole or just dig a hole big enough to bury the entire basketball hoop base.
My neighbor decided to just dig a hole big enough to bury the entire basketball hoop base instead of removing the base.
My neighbor has a backhoe so he dug a hole in the yard deep enough to bury the basketball hoop base and it worked just fine.
He just added dirt to the base of the basketball hoop and buried it in the ground and then he didn't need any concrete to hold the basketball hoop in the ground.
It worked great by burying the portable basketball hoop so I had him bury our portable basketball hoop as well and I never have to remove it and we put a concrete pad in the backyard so the kids could use the basketball hoop in the backyard instead of the driveway away from the road.