Romhacking.net is going strong, rom hacks are by definition non-commercial and underground.
Newgrounds of course as mentioned.
(edit: I want to include Pico-8 too though I wish it was updated more and was even bigger than it is!)
I very much support your initiative; I think you're just vocalizing something many people can feel which is that the entire industry has raced to the bottom and the players have come to expect a bait-and-switch from every product that they see. People want art and innovation, but they can't be expected to dig through the crates in the back of the record store to find it. We should be the DJs who bring those records out of the crate and play them publicly somewhere.
I think a platform dedicated to completely unmonetized games could be a reasonable starting point for that. But how do you pay for a platform dedicated to free stuff? the age old question :) Might need some wikipedia-level community contributions to make something like that work.
(Edit: and to touch on your original point of "Underground" vs "Indie" I think part of the issue is that the non-Indie industry is using the "indie" label for games made with teams of 20 people lol)
Ty. I agree that RomHacking is inherently underground (same is true at least for parts of the modding community). Yet they (again: Like the Modding community) are a bit stewing in their own juice. Until now this works for them - but modern gaming industry is showing both groups the teeth, and most contemporary games are harder to mod or hack, making the hobby less attractive for younger players.
Maybe I'll have to take a closer look on Newgrounds, regarded them mostly as some flash-game hub until now ;). Lately I'm fishing a bit into the web revival scene - a lot of creativity is bundled there right now.
The idea of creating platform occurred to me as well, but I think that Itch is doing a fine job for hosting projects - what we rather need is - imho - more communication between ambitious developers and more (external) curation.
Yes, the "commercialization" of indie gaming is definitely a part of the problem - on the other hand, there never was much resistance against it, so I think that this was bound to happen, and that only a distinction from commercial gaming can create a staying and interesting scene.
Guess you made more than the project linked to your account? If you want, mail me some links to your games and I'll gladly look into them.
contact [at] thunderperfectwitchcraft.org