via make.wordpress.org => original post link
Back in August, 2020 a Gutenberg issue proposed the following enhancement:
It’d be nice to allow to have fluid typography option so that design would look good on all viewports. This would open the door for designers to make a more bold visual expression that’s difficult to do with fixed font size.
An experimental pull request (PR), Block supports: add fluid typography #39529, puts forward a way to realize this enhancement by allowing theme authors to enable fluid typography across their site.