Model file formats such as LP and MPS files are processed under the assumption that all content, including variable names and constraint names, is written using ASCII characters. Therefore, Gurobi does not guarantee the proper functioning of files containing characters outside the ASCII range (even single-byte characters) such as "ß", "→", and so on. Even if it works as expected in one environment, it is probably environment-dependent and may not always be interpreted as intended; therefore, such usage is not recommended.
The same applies to the Gurobi API for each programming language. It is recommended to use only ASCII characters when specifying attributes and parameters, including input/output file paths or filenames. As an typical example, when you instruct through gurobipy to write (or read) the model file "Weiß.lp" by using Model.write() (or Global read()) method, it may yield an error such as:
gurobipy._exception.GurobiError: Unable to write to file 'Weiß.lp'gurobipy._exception.GurobiError: Unable to open file 'Weiß.lp' for input