Aside from the new security patch level, it appears the very build numbers attached to the packages — G950FXXU9DTF1 and G955FXXU9DTF1 — also appear to be alluding to some other novelties. As for the specifics on those changes, they'll likely stay under the radar until Samsung accompanies this over-the-air deployment with an official changelog or two.
Galaxy S8 series nearing well-earned retirement
In spite of the long life cycle, the Galaxy S8 family is now at last nearing its well-deserved retirement. Samsung hence downgraded it to quarterly updates this spring, though it appears at least some regions won't be adopting that slower schedule until at least next month, as the appearance of the June 2020 patch indicates.
Any owner of a Galaxy S8-series smartphone who's feeling particularly impatient can always attempt triggering the latest security patch upgrade manually through the Settings app, i.e. its Software update submenu concealing the Download and install option. Alternatively, the newest official system images are also available for download from SamMobile's firmware archive.
