There are plenty of itch.io alternatives, although itch.io and IF Archive are the ones generally used by this community. You’ll notice older games on IFDB generally have IF Archive links, while newer ones tend to use Itch. But there’s also Newgrounds, where account creation is just as easy as Itch account creation, though Newgrounds only hosts web-compatible game and doesn’t allow downloaded files.
Newgrounds is a very old site, but it’s still alive and kicking. It hosts games, art, and animations. It does have a policy where games have to be “approved” before you can see comments and ratings on them, typically through a few older members playing through and rating the game to confirm it’s not spam. It takes a few days, but it’s not much of a barrier to hosting. I think Newgrounds isn’t as popular here because Itch has the “game jam” feature that a lot of newer jams and comps now rely on, but that’s just a guess. There are a few IF games hosted on Newgrounds, like Missed Messages (IFDB link).
If you’re a bit techier, there’s Neocities and Github Pages. Any web-based game that doesn’t rely on sound can be hosted on Neocities. You can’t put audio or video files onto your Neocities website without becoming a paying member. Actually, Neocities limits the types of files you can upload to your site if you’re a free member, which makes it very impractical to try hosting downloadable IF games on your Neocities site. The full list of allowed filetypes is here. Social Democracy: An Alternate History (IFDB link) and the other Social Democracy games are mirrored on Neocities.
Github Pages has no filetype restrictions but is slightly more complicated to set up than Neocities. On the other hand, any web-based game or downloadable file can be hosted on Github Pages. These two platforms generally come with less discoverability, so you’ll have to spread things through word-of-mouth. Though that applies to all these sites anyway. Biennio Rosso, a Social Democracy fangame (IFDB link), is hosted on Github Pages. So is Nyoperativsystem (IFDB link), and probably a lot of other obscure games I haven’t played.
There’s also Gamejolt, for downloadable games, although I haven’t used it before. When I checked in on it, it seemed to mainly be known for Undertale fan games and the like (Undertale Yellow is hosted on there for free. Very fun game), but there’s no reason why you couldn’t put your own downloadable files on there. I’m not aware of any IF games hosted on Gamejolt, but maybe some exist.
Steam is the nuclear option, but since this is a hobbyist community and I believe the fee for putting a game on Steam is a hundred dollars, it’s not used for many games. But there are some large ones, like Hadean Lands (IFDB link), that have Steam listings.
The last resort is to just purchase your own domain and make your own website. A lot of popular web games and IF like A Dark Room (IFDB link) do this.
Those are all the big options I’m familiar with. There are definitely other various hosting sites out there, though. And a lot of older ones like philome.la that are no longer accepting new submissions.
You’ll notice a lot of the games I linked here are hosted in multiple places. Missed Messages is on Itch, and Newgrounds, and Steam. This is the best way to maximize discoverability, and it provides backups if one of those sites goes down, so I’d recommend it.