Apple has just released the third beta of iOS 13.3, unlike the previous one, Apple only offers the version for developers. The members of the beta-testing program will have to be a little patient.
This is a third beta, so there are not really any new features except improvements and fixes.
As a reminder, iOS 13.3 will allow Safari to support 2FA, NFC and USB keys. There are also new features to limit communications in Screen Time, as well as disabling Memoji stickers in the virtual keyboard. Nothing exciting about it, but this new version could make significant corrections for bugs detected on the current version of iOS.
It is possible that Apple will introduce other notable new features through the beta versions, but it will take patience to discover them.