Matthias, on May 3, 2020, I confirmed you that the solution worked. It was Issue 128298
In my mail I said:
"I installed hunspell and now it works fine.
However, hunspell was not included in the list of required libraries
in file read1st.txt which is part of the distribution."
This was corrected in the 4.1.8 distribution.
Thanks
Eduardo Vila Echagüe