You cannot rename a file from webp to jpg, but you can change the URL to .jpg and it will likely serve you the jpeg version. You can also convert webp to another format with dwebp or MS Paint.

threads.net is the domain. You can get a head start and block any IP addresses associated with it using the firewall of your choice.

This is a common result of firm firmware and tinkering.

Extra firmware cannot be modified.

Firm firmware might be able to be modified, but documentation is largely unknown.

Silken firmware is easily modified by the user.

These names are taken from tofu packaging.

Like Pixelfed?

I would recommend making a full git repository and at least adding a license header so that others can expand upon it. Maintaining a useful gist is cumbersome as issues tend to be ignored comments.