I would like to know if people need visa to stay more than 3 months in the UK during the transition period. My friend is planning to travel there for 6 months. He is spanish.
An EU citizen wishing to travel to and remain in the UK for any period of time may do so during the transition period (currently until the end of 2020) in the same way as when the UK was a full EU member.
If you’re an EU, EEA or Swiss citizen What you’ll need to enter the UK will not change until at least 2021.
You can always use the following website to check if you need a visa or not (for any nationality)