Here in the UK they are illegal (unless used on private land), which is sad as whilst they are illegal as technically a motor vehicle, needing some form of test, insurance, mot.... That has not happened and in limbo as clearly a need for some standards control etc, but an unwillingness to address that and more so a periodic fashion stopping of people upon such vehicles in an apathetic way that causes many to get one, go months, even years without knowing they are breach of the law and driven past many police/traffic wardens, then suddenly one day they stop you and caution you saying you can't. They then go back to ignoring it as a low-priority issue and the limbo of not legal as no formal way to allow one, yet readily sold and accessible.
So for the UK, such rise is randomly curtailed and no progress upon legal avenues to use them as you would intend beyond private land - which many do not own in London, an area in which such modes of transport are most suited.
[EDIT ADD] A better read upon what I said :- https://www.bbc.co.uk/news/uk-48106617