Legend Quest is both more and less restrictive on teleporting than that other game (at least the editions that I played). First - It either works or it doesn’t. There is no “do it and then figure out how dangerous it is to your life”. If there is something in the way - you don’t die, it just doesn’t work. But because it requires a hefty fatigue (especially long range teleporting), it can knock you out, and even kill you (you being the caster, even if you are not the one sent).
So when you teleport into a space, there needs to be nothing in the way. But obviously, there is gas in the way. I usually assume that the arrival causes a sudden rush of air, because the person is displacing the air that is there. Similarly, the place the person left would likely have a “pop” as the air rushed into the void left behind. Now on Fletnern, long range teleporters establish “receiving platforms”. They all know each other’s platforms and they send folks to friendly teleporters in other cities. This works because that person who just arrived probably wants to teleport back and now they know just where to get that service. The platforms are kept clear so incoming folks have a safe place to arrive.
If teleporting can displace gas, can it displace water? I don’t think so, but if I had a merman who teleported, I would probably assume that his was different. Can it displace smoke? Probably - Smoke isn’t that different from air. What about bugs? Would a teleport fail if there was a mosquito flying across the “landing zone”? I guess not, but that would make a funny issue: New Mission - find a way to save the ambassador who teleported in and now has a horsefly stuck inside his chest. What would be the maximum mass/weight that can be dispersed without incident vs. causing a failure?
I would think stretching a net across the landing zone would prevent folks from teleporting in. If blocked from teleporting in, I normally assume that the caster could then send people to a “safe place”, but what is that? Would a grassy hill be safe? No, because the grass would be in the way, unless you teleport them higher than the ground, but grass can get pretty tall. Over a river or pond? Yeah - safe, but messy as the person now splashes down. Anywhere public has too high a chance of people being in the way or even if they are not, then the risk of startling too many. Most of my cities have laws about teleporting, because you are effectively smuggling (avoiding taxes). That plus they don’t want you teleporting in assassins and other threats, but let’s face it, that is part of the business.
I think high fantasy requires this style of magical service, but you can’t make it easy.