> Prices rise due to increased consumer spending capability, to the point where you have to work again to get above the poverty line.
Governments will respond to economic factors that diminish purchasing power in order to maintain the effectiveness of UBI, as a part of UBI.
> Any realistic UBI is too low for people with special needs
Diminished support for disabled or sick people is not a part of UBI. UBI should become a part (within or on top of) of their support. Bureaucracy will still be diminished for non-disabled people.
> If the UBI is independent of local cost-of-living, it'll most likely be too low to survive on it in high COL areas
So people in those areas will have to have jobs. UBI still allows them to go quit their job and move out to the country if they want to subsist on it. UBI would go nicely paired with rent controls and maintaining individual purchase power, but it doesn't even need those things to be a net positive.
UBI should have been implemented 20-40 years ago, it will surely be necessary going forward, it's time to get on board.