This is information for UK citizens with residency in Spain, that still use their UK driver licence to drive in Spain.
Due to Brexit the rules for UK residents to change a UK licence to an EU Spanish licence have changed. It has become much harder to get your UK licence changed to an EU Spanish licence, including a driving test, beside the already installed medical test that is compulsory.
Due to the many applications to change licences, the DGT, Spanish driver licence authority, has a delay in processing these. So an extension to get the paperwork in place is needed.
In the case that you have arrived to live in Spain after 01/01/2021, then your UK driving licence is valid for just 6 months from the date of your TIE or until 31/12/2021.
If you are a British tourist with UK licence on holidays in Spain this does not affect you. So as a tourist you can just rent a car for your holidays. As long as you stay in Spain for less the 3 months.