In the UK, the spots are allocated to parties rather than candidates, and determined by past election (and to a lesser extent, current opinion poll) performance.

https://www.ofcom.org.uk/about-ofcom/latest/media/media-rele...

Put that Wikipedia article through google translate, I'd suggest. Depending on the broadcaster different legal requirements apply - but generally if you are big enough to have a full statewide candidate list you're eligible. Different states allow for lower limits than this, and if you're refused you can file a legal complaint.