Yeah, Brazil has decided to no longer follow DST. DST won’t start on the first Sunday of November 2019 as previously scheduled.
I suggest you to open a ticket so that WordPress devs can fix this situation:
https://core.trac.ww.wp.xz.cn/
WordPress doesn’t actually have a list of timezones in it, so making a core ticket won’t help you.
WordPress uses the built in PHP functionality for timezones, and this itself relies on a system called “zoneinfo DB” or “OlsenDB”. You can find more information about it here: https://en.wikipedia.org/wiki/Tz_database
In order for this information to be updated, the database must be updated with the new information, and then your server must receive these updates. This means that you will need to take it up with your hosting service. While PHP itself updates to the latest version of this with every release, there is also other methods for keeping this updated externally, such as PECL updaters for it and the like.
WordPress itself does not include a copy of the timezone database, it relies on the hosting service to keep that up to date.
