Stores with keys without region lock

The thing is, the restrictions are mostly from the publishers so nothing you can do about that. Unless if you want to directly go to the publisher to buy the row keys, of course.
But some games will have row keys depending on the publisher. I believe you can check it from steamdb to see if they have some region locked packages. If they don't have it, you can assume they only sell row keys to third party sellers.

Also, if you check the deal thread, especially an older one (1-2 days after release should be safe) and see bundles that have no lock, it is mostly a row key. If it is not, then nobody reported it yet (and please help to report it for others)

My (limited) understanding is that region restrictions depend on the game, not the site where it's purchased from. If a publisher decides to put restrictions on a game key for a certain country, those restrictions will be in place no matter which site you purchase the key from. This is to prevent, for example, people from US buying up keys from countries where they may be sold for less because the economy is weaker. But not all games have region restrictions.

You can try with Eneba(dot)com . I have bought around 30 keys there, including some of my giveaways, and still hasn't got an issue. The thing is they take a little fee from any conversion between currencies. So it's best to add like 20 bucks or more in funds. They don't have bundles like Fanatical or Humble, but they've got good prices.

I changed category to General, Help is to ask about SG issues or rules explanation. And this is general question about key giveaway source.

Bundle deal threads here will generally list any potential issues with region locks. As in "people from this country will get region locked key". It depends on the publishers how they set it up, some games don't have any region locks at all.

You can try to check deeper by visiting game SteamDB page. Say this one:
https://www.steamgifts.com/discussion/SMJJl/humble-bundle-spaced-out

https://steamdb.info/app/578650/subs/

When you click on subs of game you will see that they are region locked:
https://steamdb.info/sub/509790/
https://steamdb.info/sub/509791/
https://steamdb.info/sub/509792/

If you try to buy game, and see sub with region that includes your country - it is likely key will be region locked for you if it's bought on Humble, GMG, Fanatical etc. It would be good if Shop would supply info which subID it will activate. But they don't.

I had similar problem, cause even when I live in expensive region, these stores started lock my keys to Europe. I am trying to buy keys for giveaway at Games planet,which always confirmed me their keys are global with exceptions listed at games (and Russia/Belarus for obvious reasons)

Since you listed Brazil as your country on your Steam profile, I assume you're visiting the stores (HumbleBundle and Fanatical) with a Brazil IP as well?
At least for these two sites I can say that you'll get region restricted keys all the time, if there are any. You can check on steamdb.info if there are any packages which are region locked. If there is no region locked package listed, it's safe to assume that the keys don't have a region lock (maybe in one out of 100 cases steamdb is wrong according to my experience).
It's also possible that half of the games of a bundle are Global keys and half of them are region restricted.

Reason behind this are the prices for games in general. Keys which are restricted to Brazil for example, mostly can only be activated in other South American countries - in some cases combined with other countries where the prices are lower in general (like Russia, China, Turkey and so on).

The only solution would be to use a VPN and change your country to USA or some European country for example (since these keys are Global mostly) to buy these bundles - if it's allowed on Humble Bundle, Fanatical and so on, you have to find out yourself (you can read that in their Terms of Use I think).

Another solution you can try: Writing the publisher, if they could send you a Global key. For me this worked twice already (once for a game from Devolver Digital and the other one from Daedalic). They wanted my key and some proof of payment, but in the end I got a Global one. But personally I think only "smaller" companies are forthcoming like that if at all. In case of huge publishers I think this solution will be nearly impossible.
Also I think it will depend on where you buy these games, since they will only replace keys from official stores.