[yellowapple]

> Could that really work at a local level where people can freely move cities? Local UBI seems hard to implement in a non city state.

Only if you overthink it. An "open border" LVT+UBI system is self-balancing; a flood of immigrants would drive up demand for land, which drives up its value, which raises LVT revenue, which raises total UBI disbursement, which keeps each individual's UBI stable.

That said, it would work even better at a state level, and better still at a national/federal level.

> why not take the Singaporean approach?

The Singaporean approach (IIUC) includes land leases, which is in practice equivalent to a 100% LVT (assuming the government prices the lease at the land's full value).