Where are those giveaways coming from?

New bundle, both games are part of the Humble Play Pink, The Best Of Asmodee Digital Bundle
https://www.steamgifts.com/discussion/JTsjh/humble-bundle-humble-play-pink-the-best-of-asmodee-digital-bundle

Indiegala challenge most likely.
Similar to their games roster

fanatical.com
dollar neon bundle

0,17$ - gamesforfarm

https://www.fanatical.com/en/bundle/the-game-creators-bundle

Might be leftovers from the January 2021 choice.

Are you Blind? It say it in every Shelter Manager GA!
"Our new game just came to Early Access!"
"Please support us by wishlist and adding to favorits ;)"

So those are from Dev.

Certain russian key shops

Indiegala ✔

Hidden Art 2 Bundle
■ Ended 3 days ago

Fanatical Mystery Boost Bundle
mehh

June 2020 Humble Choice #7

https://www.steamgifts.com/discussion/c3ERb/humblebundle-classic-subscribers-can-claim-2-more-games-from-2020-choice-bundles

Here is the reason : https://www.reddit.com/r/humblebundles/comments/qchcf0/if_youre_a_classic_sub_claim_these_asap_it_seems/

Fanatical ✔

Mystery Boost Bundle
▶ Started 3 days ago

for Shoppe Keep 2 - https://www.fanatical.com/en/pick-and-mix/build-your-own-simulator-bundle
for Niche - https://www.fanatical.com/en/pick-and-mix/platinum-collection-build-your-own-bundle

Most keys are actually from old Humble Choice selections.
Shoppe Keep 2 is from April 2020 Humble Choice #5
Niche is from May 2020 Humble Choice #6

Because of a bug people could claim two more games from older Humble Choice months yesterday. SG and reddit topics on it are linked a few messages above here.

Fanatical - Mystery Boost Bundle

found it, it's 2 EUR on Humble store

https://www.steamgifts.com/discussion/3dUu8/humble-bundle-fighting-juggernauts-bundle

Here is the reason : https://www.reddit.com/r/humblebundles/comments/qchcf0/if_youre_a_classic_sub_claim_these_asap_it_seems/

Loophole/Bug has been closed by Humble.

giveaway dot soviet union.

https://www.steamgifts.com/archive/search?q=shelter%20manager

All made by one person (developer)

Description in every GA:

Our new game just came to Early Access!
Please support us by wishlist and adding to favorits ;)

So dev themselves

Lootboy Balenciaga diary pack