Do tech companies offer sign on bonuses / new hires get them?
It is also useful to mention any other offers you may have and to apply for other positions, even if you're less interested in those roles. A friend of mine applied for several roles using that strategy including one he thought he'd be totally uninterested in. He wound up being most excited about that role after getting further along in the process and ultimately accepted it, even though he intended to only use it as a bargaining chip.
You also can apply for other roles and even mention "I'm early in the process, but they've stated the usual comp range is XYZ, which is higher. I'm more excited about this role, but it could be hard to turn down that kind of compensation".
I'd just ask and see what they say?
The only thing I'd point out is that you should be sure you're willing to walk away from the opportunity they're offering you, before you push too hard. You need to be okay with them saying no to your terms.