According to Budapest Airport’s website announcements, there are new regulations for people flying from Hungary to the Netherlands as of the 23rd of January, 2021.
Passengers over 13 years of age are only allowed to board the plane if they have a negative PCR test not older than 72 hours AND a negative quick antigen test done within 4 hours before departure time.
There are exemptions that apply (e.g. NATO travel orders), please read through the following regulation: Mandatory negative COVID-19 test results and declaration | Coronavirus COVID-19 | Government.nl
The airport testing point is open from 03:00 until 20:00 every day to make sure all passengers have the opportunity to get the antigen test done.
For more information on the test center at the airport, please see the following post: Budapest Airport COVID-19 testing center – Insite Pápa (insitepapa.com)