Does Humble provide client-free, DRM-free, direct portable downloads? Or is it steam keys and such?

A few, yes. I don't recall if portable though.

They do have some DRM free content but it has been vastly overshadowed by selling keys for clients such as Steam , Uplay, and Origin.

Edit: my link completely broke formatting...
Ok, I fixed it.

Support article from Humble Bundle

They used to provide proper DRM-free downloads i think but by now they turned into a key reseller. They still have (a few) DRM-free games, but mostly you're getting keys from DRM-infested stores. That's part of why a lot of users here freaked out so much about Galaxy selling Epic Game Store games. They're afraid that GOG will turn into the same thing.

Both.

The few DRM-free downloads they provide are usually portable, but it depends on how the developers packaged them. Some may be actual installers (not just simple zip files or the like) AFAIK.

They also provide GOG keys.

This statement is technically true.

Hypothetically, true.

The reality is false, Humble is basically a glorified steam key reseller in this day and age.

Itch.io is more to what you seek.

The Humble store has over 1400 DRM-free games available.

Thanks.

Do be aware, all the above is true, they have some drm free games (some you can’t get elsewhere like tinman games set). But it has been dwarfed by the key selling. Games are also not necessarily the latest version, and may be lacking some dlc. Bioshock is there for instance, original not remake. There are some you can’t get elsewhere, I was pointed to this game recently:
https://www.gog.com/forum/general/glare_pc_game

They do both. You can even buy DRM-FREE titles directly from their store outside of their bundles.

https://www.humblebundle.com/store/search?sort=bestselling&hmb_source=store_navbar&drm=download

You can also do cash back with all of their direct store purchases.

I use to like these options myself but I recently removed my account from their store.

Exactly zero of the posts in this thread tried to make it sound like a "bastion of DRM-free". As others said, they do mostly resell Steam keys. But you can filter by DRM-free in order to weed out all the Steam-reselling nonsense, in which case you see the majority is stuff already on GOG. But there are some worthwhile exceptions, like the Mac + Linux versions of the Metro games (not Exodus sadly), Antichamber, and some others.