FYI, FWIW, the plugin is still being offered in the Debian 12.2 repository on my MX Linux distro. Here's the repo listing as shown in aptitude:
i --\ geany-plugin-markdown
Description: markdown plugin for Geany This plugin provides a real-time preview of rendered Markdown in Geany.
Geany is a small and lightweight integrated development environment using the Gtk+ toolkit.
Homepage: http://plugins.geany.org Tags: uitoolkit::gtk Priority: optional Section: devel Maintainer: Geany Packaging Team pkg-geany-team@lists.alioth.debian.org Architecture: amd64 Compressed Size: 523 k Uncompressed Size: 605 k Source Package: geany-plugins Label: Debian Origin: Debian:12.2/stable [amd64] Origin URI: http://deb.debian.org/debian/pool/main/g/geany-plugins/geany-plugin-markdown... --\ Depends (9) --- geany --- geany-abi-18432 --- geany-plugins-common (= 1.38+dfsg-2) --- libc6 (>= 2.4) --- libglib2.0-0 (>= 2.37.3) --- libgtk-3-0 (>= 3.3.16) --- libmarkdown2 (>= 2.0.6) --- libpango-1.0-0 (>= 1.14.0) --- libwebkit2gtk-4.0-37 (>= 2.5.3) --\ Enhances (1) --- geany --\ Conflicts (1) --- geany-plugin-markdown --- Packages which depend on geany-plugin-markdown (2) --\ Versions of geany-plugin-markdown (1) i 1.38+dfsg-2
And now, after reading the preceding (March 6, 2022) comment by "eht16", I finally understand why the plugin fails to render previews. Darn it. I was pretty psyched to have Geany double up as a live preview Markdown editor.