Hi Emiliano
Greetings from Syncfusion.
We have validated your query and we are able to reproduce the reported problem. We have confirmed it is a bug and logged the defect report “The filterbar dropdownlist does not appear properly in fabric theme”. Thank you for taking the time to report this issue and helping us improve our product. At Syncfusion, we are committed to fixing all validated defects (subject to technological feasibility and Product Development Life Cycle ) and including the defect fix in our upcoming weekly patch release which is expected to be rolled out on 5th Aug, 2020.
Until then we appreciate your patience.
Regards,
Vignesh S