Thank you for your answers.
What I have found is the following:
Disable or enable spellcheck in Edge or Chrome has no effect on PB web browser spellcheck.
Users with internet connection have spellcheck and users without internet connection (reach only local servers) have no spellcheck.
Navigate PB web browser to chrome://version to see the command line parameters.
I found that the default langauge is english: --lang=en-US.
The dictionary file is located in this folder: C:\Users\username\AppData\Local\CEF\User Data\Dictionaries\en-US-8-0.bdict
Running the deployed exe with a given lang parameter (i.e --lang=hu-HU) we can change the loaded dictionary file.
The given dictionary file will be downloaded and used for spellcheck.
To disable spellcheck in the PB web browser run the deployed exe with the following parameter: --disable-spell-checking
Best regards, Tamas