Yeah, that’s expected for now. When UniFab burns subtitles into the video, it uses a default font and there isn’t an option to change it yet.
A workaround would be to style the subtitles beforehand (for example with tools like Aegisub or Subtitle Edit), then load that styled subtitle file into UniFab for rendering.
We agree this would be a nice feature to have — custom font support is definitely something worth adding 🙂