The vortex-sfm project is intended to simplify managing external assets for SFM (for non-Workshop content) using Vortex. This allows for installing external models, maps or any other supported content as a Vortex-compatible mod.
Full details of the extension project and how to get started are available at vortex-sfm.silveredgold.vip
The project has been rewritten to remove the need for multiple Vortex extensions and the USPU tool has now been deprecated in favour of a new feature included in the latest versions of the Vortex extension (thanks agc93 for helping out).
This extension is the primary focus of the project. The extension adds SFM as a supported game to Vortex where it can be maanged like any other Vortex-managed game. Since Nexus doesn't support/host SFM mods, you won't be able to use the Nexus-specific Vortex features, but you can download and install ZIP archives (including from SFMLab). Click "Install From File" to install your SFM "mod". Check the Mods tab in your Vortex settings to control the default install type and to enable automatic search path handling.