The weewx-meteotemplate extension is still perfectly usable, even though the Meteotemplate project itself is gone.
I have written WS40, a self-hosted WordPress plugin for personal weather stations, and it implements an endpoint compatible with the Meteotemplate API dialect. That means Matthew Wall's uploader works unchanged — no fork, no patch. In weewx.conf you only change two values:
The rest of the configuration stays as it is, and the upload runs alongside Wunderground, CWOP, PWSweather or anything else you already have enabled.
Disclosure, since it matters here: I am the author of WS40 and I acquired the meteotemplate.com domain after the project closed, to help its users land somewhere maintained rather than lose their setup. The core version is free and published on the WordPress.org plugin directory as "WS40 Live Weather"; there is also a paid tier. I am not asking anyone to switch — I am posting because the extension is still in the wild and people were asking where it can point now.
Happy to answer technical questions, and if anyone wants to test against a live endpoint before committing, just ask.