This simulated FLEX data was provided by ESA. To access the dataset, you need to connect to the ESA FTP server. Use the explanation provided in the published document "[PDF] Explanation & access to the simulated FLEX data" as support. In chapter 6 "DATASET ACCESS" you will find the server path and the login details.

This dataset consists of HyPlant FLUO at-sensor radiance measurements from different campaigns in the years 2018 - 2023, FLOX measurements corresponding to several campaigns and matching SFMNN and SFM SIF products. To download the data, click on the link under "Storage Location URL". You can also find more information on the dataset here