I don't know if miners are against it, but I can think of one group that wants it to fail: big blockers, with Bitcoin Cash shills at the forefront. I visit their reddit now and then and they always find reasons to shit on it. It's easy to see why, too, since the Lightning Network seems like it can kill Bitcoin Cash altogether.
As for obstacles, I don't think there are any. Transactions have been completed in it after all. It's probably just a bunch of dev work and rigorous testing at this point. We're talking about money here, so it would have to be flawless.
The biggest obstacle I see is how to sell people on Lightning Network when it isn't a decentralized system. This to me will be the hardest problem to overcome but there are several different problems pick your poison.
Does it make bitcoin whole network centralised permanently or is it a centralised off chain layer temporarily centralised when lightning transaction happens?
Or what scalable solution is available for bitcoin out there that is not centralised?
Just the off chain layer. It doesn't even necessarily have to be centralized. There could be multiple payment channels owned by multiple groups. They also can't do anything to the transaction other than to facilitate it either, to my understanding. I don't believe this to be a problem.
I don't know of any other solutions. Even bigger blocks lead to centralization.