Have you checked out the stuff that Adafruit has on Github. They seem very excited about SAMD5x, and apparently have made a bunch of progress already. I'm not sure whether that includes floating point considerations.
(It looks like a really promising set of chips. I like that it goes from Uno-sized to Mega-sized without major changes (unlike Zero vs Due.))
(Or "will", anyway. Atmel has never been particularly trustworthy in the "delivery schedule for new chips" department, and I doubt whether Microchip has fixed everything. There are currently a fair number of people upset about the Atmega328PB becoming "unobtainium.")