Where are those giveaways coming from?

Maybe from that Twitch channel. It also has been under 4€ on grey market sites for months and currently costs less than 3€.

Someone said fanatical, it's true on reseller sites it's 3 euro.

https://www.steamgifts.com/go/comment/nD9PXmo

CDkeys £2.49, ended I'm afraid though.It's still available on other grey sites for around 3 euro's as Lugum mentions.
Prices on GG Deals

https://www.steamgifts.com/discussion/1zP0R/humble-bundle-deck-builder-bundle

There was a giveaway on igames gg 6 hours ago.

source: https://www.reddit.com/r/FreeGameFindings/comments/w7xhr1/steam_game_crescent_hollow/

~500 keys? 300?

I'm guessing all gone within a few minutes back then.

From the HitSquad's Twitch channel (ended or I'm unable to find that there. But in Discord I see that they gave it away for some amount of channel points)

Most likely from the newest bundle:
https://www.steamgifts.com/discussion/EBVkb/fanatical-killer-bundle-23

Most likely from the newest bundle:
https://www.steamgifts.com/discussion/EBVkb/fanatical-killer-bundle-23

https://www.steamgifts.com/discussion/p8CUv/fanatical-bento-spirit-bundle

https://www.steamgifts.com/discussion/viSSG/humble-bundle-amazing-adventures-bundle

probably old groupees bundles leftovers

I can confirm that pb1 is correct. It is where i got it from when i made a giveaway a month or so ago and two of the three most recent giveaways have also been old groupees key as in the description in their giveaways.

Dreamfalls Chapters:
as answered 2 posts above https://www.steamgifts.com/discussion/viSSG/humble-bundle-amazing-adventures-bundle

legion td 2 is from https://www.steamgifts.com/discussion/YpQOY/humble-bundle-july-2022-humble-choice-32

alienwarearena

Excellent, thanks for the heads up.

alienwarearena

https://www.steamgifts.com/discussion/HPXFl/humble-bundle-august-2022-humble-choice-33

humble choice august

August 2022 Humble Choice

opquest

from twitch, there's a user that gives a ton of them, hitsquadgodfather.

Fanatical Build Your Own Triple Pack

My copies are from the mystery bundles from fanatical.

Humble
https://www.steamgifts.com/discussion/oPtbS/humble-bundle-the-walking-dead-10th-anniversary-bundle

https://www.steamgifts.com/discussion/tPzC3/alienwarearenasteam-battletech-no-restriction

HB August Choice

givee club - ended