I run a small imageboard on my personal computer that can be reached via Tor, I2P, and Yggdrasil. It's mostly focused on math and technology, but other topics are welcome. There are a lot of threads about solving puzzles, steganography, formal logic, software verification, privacy, and image / video compression. Pic related is the catalog on /All/ so you can see what kind of threads are there.
http://lambdaplusjs35padjaiz4jw2fugdoeutse262phqr72uf634s2wdbqd.onion/All/http://l7jqnz3yfe2wtwietafoieadmgqbu7dcmzmey63ktbjtxal3he4a.b32.i2p/All/http://[200:e111:a7c7:6fee:8a1b:90a7:2b17:79ec]/All/I wrote the software myself. I started working on it after nanochan, another Tor imageboard, began failing. The design draws a lot of inspiration from that site and its picochan fork. Namely, despite the name, there is no use of Javascript anywhere on the site, yet features like a floating reply dialog and inline image expansion still work.
I also copied 4taba's idea of creating boards by just navigating to an arbitrary /board/ name. Like 4taba and unlike 8chan, all boards are managed by the admin; the person who effectively creates the board by making the first post to it has no more power or authority than any other user. Moderation works primarily by moving threads or posts (often to less visible boards) rather than deleting them, although CP and other attempts to use the board to commit crimes are outright removed. There's a public log where you can view all mod activity.
Other notable things about the board / software:
- Open source,
http://lambdaplusjs35padjaiz4jw2fugdoeutse262phqr72uf634s2wdbqd.onion/Source/- Any file type can be attached to a post, although only some are thumbnailed and can be viewed in the browser, while others trigger a download. SVG, AVIF, and JPEG XL are among the file types with thumbnail and inline expansion support.
- Multiple files per post are supported.
- Markup is minimal to avoid breaking source code, but includes quoting and spoilers. Indentation is preserved by default, so no need for code tags.
- Backlinks work across threads and boards.
- Normally no captcha is required to post, but occasionally when the post rate gets very high (usually due to someone spamming), the captcha is automatically temporarily enabled.
- Screenshot shows the light theme, but there's a dark theme as well.