Pixelmon Reforged is a continuation of the original Pixelmon mod by the original developers. It is being continually updated and many servers are using it. Here is a quick overview of how to install Pixelmon Reforged:
Using the technic launcher is by far the easiest way to install Pixelmon Reforged.
1) Download and install technic launcher from here: https://www.technicpack.net/download
2) Once installed, visit this page and click "Install" at the top: https://www.technicpack.net/modpack/pixelmon-reforged.1150447
3) Run the pack!
1) Visit this page and download Pixelmon Reforged: https://reforged.gg/
2) Download Minecraft Forge (installer) from here: https://files.minecraftforge.net/. As of now, Reforged is built on Minecraft 1.12.2. This may change in the future, so you will need to look at the Minecraft version listed on the Reforged website in order to download the correct Forge version.
3) Install Minecraft Forge by running the installer.
4) Place the downloaded Pixelmon Reforged into your .minecraft/mods folder in %AppData%
There you go! Now to get online with some servers you can check out all the servers running the latest Pixelmon Reforged version here: https://pixelmon-server-list.com/version/Reforged%206.2.1