With the aid of this optional add-on, Instiki (and this forum) can process embedded Tikz code to produce SVG figures. Think of it as a non-WYSIWYG alternative to SVG-Edit. You can get the code from Github.

The easiest way to run it is as a Docker container. The Docker image is 2.14 GB, which is on the large side, but not as large as a full Texlive installation. Instructions for integrating it with Instiki are here.

Actually, with tex2svg 1.0.12, the size of the Docker image has shrunk to 1.09 GB.