There are no "fluidsynth soundfonts". Fluidsynth loads sample libraries ("sound fonts") in the SF2 format. There's nothing unique to Fluidsynth about them - dozens if not hundreds of other tools can load them.
I am not sure why you'd mention Timidity in this context. Using fluidsynth (or more likely, a GUI front end for it like QSynth) would in 2021, be a more straightforward approach, I think.
I would also mention DecentSampler in this context. It is not libre software but it is gratis, and it will give you easy access to playing with dozens to hundreds of the growing number of libraries on
pianobook.co.uk (most of which, even the worst, will be notably more expressive than typical SF2 libraries).