Flstudio by default like all the other 'Fruity' plugins, I'd NEVER heard of it being a standalone thing you had to buy.
In the trial version of FL it was using soundfonts just fine, and I've seen ...
FLStudio 20 Fruity Edition, and tried to open a project that had used Soundfonts. It tells me my patterns will be locked, as they had previously used the Fruity Soundfont Player. I would love to buy Fruity Soundfont Player ...