Change of displayed name does not work

[BrainOn]

Hello. I would like to effectively set my display name for all meetings to just my first name. This is already set in my Profile settings on the web client. Nonetheless my full name with family name is shown in all zoom sessions. I already read all the instructions to change the name and checked all settings, they are correct as far as I can see. Is there any other, hidden option?

Thank you all.