Grantapher has released an unofficial fix on the official Github repo of ValheimPlus (look through recent pull requests and issues) and someone also released ValheimPlus Fix on Nexus. Make sure to take regular backups of your characters and worlds if you plan on adding/removing mods.

From what we know, the ValheimPlus official dev is alive, he's just ignoring the community as a whole and taking Patreon's money. He did not even make a statement and his last activity was in december 2022...

I've just released a compiled version of the fix along with the Eitr Refinery and Wisp Spawner configuration added to Valheim Plus, allowing to tweak them in the configuration file: https://github.com/JF10R/ValheimPlus/releases/tag/0.9.9.13