Yes, I noticed your question 2d ago but did not know the answer, nor do we have a Stylo 3 forum to which I could have moved it. Instead I'll move it to General Help, where it may fare better.
From a quick search on the web, I don't think it's possible. That phone doesn't seem to have native support for custom fonts in the first place, so I doubt there's a way to change the font that appears when you use the stylus.
I also searched, i think its not possible. @Rukbat ... we cant write with the finger on its native application, only stylus works on it but you gave me an idea to use third party application so i definitely i will be able to use other fonts.