The BN(O) visa route offers a pathway to citizenship. After five continuous years in the UK, a BN(O) visa holder will be able to apply for settlement (indefinite leave to remain). After a further 12 months, they will then be able to apply for citizenship. 

To count as a continuous year in the UK, a BN(O) visa holder should not have spent more than 180 days outside of the UK in any given 12-month period.  

There is more information on the BN(O) route to settlement and citizenship here.