Does there exist a community contributed wiki for hiking trails?

Agreed! If it doesn't exist, I would definitely be interested in looking into hosting it myself; however, I am currently holding out on hosting a wiki until a proper federated wiki becomes a bit more established. Ibis does exist, but it doesn't appear to be seeing any development lately, so I'm not sure where they stand with it.

https://www.wikiloc.com/

But I’m not sure how open it really is.

Unfortunately, the copyright on their content is too restrictive for something that I'd want to contribute to.

The User is only authorised to access and use the Website, the Applications and the Services and to download the contents thereof for personal and non-commercial or collective use, except for the cases expressly authorised by Wikiloc. Except in those cases where expressly authorized, the User is expressly prohibited to reproduce or distribute for other purposes, as well as to transform, create derivative works of any kind, communicate to the public, make available, extract, reuse or otherwise use the Website, the Applications or the Services or any part thereof. [Wikiloc ToS §1.6]

Komoot is another one that clearly is commercial but based on user contributions. https://www.komoot.com/

It's not immediately clear to me how they license their data, but it seems to be that they are restrictive:

The user can use the offered export functions to print out associated data of necessary parts of the selected individually planned tour or export them to a target device and / or to a mobile device equipped with a chip for positioning. The user is explicitly prohibited to export, distribute or publish tours in other ways than with the offered export function. [Komoot ToS §1.4]

This is very cool! But I don't want to contribute information for only myself. I would like to contribute information for anybody to be able to use and reference.

EDIT (2024-08-09T23:22Z): I suppose one could host an instance of that for anyone to use. I'd have to think about that. I'm not sure if it would be the format that I'm looking for.

Hrm, Caltopo appears to be more of a mapping service than a wiki for hike information. Furthermore, it appears to lock most of its features behind payed subscriptions [source], and it's license appears to be a restrictive proprietary license [source].