It's October 1 and Samsung is already rolling out the October 2020 security patch, but the answer as to which Galaxy device is the first to get it might surprise you. It's the Galaxy A50 (SM-A505FN) – a very popular mid-range phone released in 2019. The update carries firmware version A505FNXXS5BTI9 and weighs a little over 123MB.
The changelog is as generic as it gets without mentioning any new features, so it appears to be just a routine update. Samsung hasn't detailed the October 2020 security patch either and there's no telling what vulnerabilities have been addressed with this latest release. Security updates usually debut without a changelog for security purposes but Samsung is likely to reveal these details by mid-October. And by that time, we expect the October 2020 security patch to become available to more Galaxy devices, so stay tuned if you own a different phone than the Galaxy A50.
As for Galaxy A50 owners, the October 2020 security update will reach more units as availability expand, so give it a bit more time if it's not available for you yet. The update will be accompanied by a notification but you can try to trigger it manually from Settings. Access Software update and tap Download and install.