As noted in another thread here, something being left on the street doesn't mean it's legally abandoned, whether it's a car, a wallet, or an electric scooter.
Most jurisdictions require the (former) owner to intentionally relinquish ownership in order for something to be considered abandoned.
No, just like you can't take someone's bicycle or a stroller if the owner isn't nearby.
But Birds, Jumps, et al, have deliberately left their scooters in public spaces for others to use. And that makes all the difference, legally.
Source: there are a dozen in front of my office and I just used one to go a block without using the app. Works fine if you're willing to use human power.
So long as you don't attempt to claim the scooter as your own (i.e., sell it), you're probably fine.
At any rate, no DA is willing to prosecute someone over this. They have more important things to do with their time and resources.
Could be a new revenue model for them when all the towns kick them out.