How to install with snap-managed OBS

[opyate]

Somewhat related to #30 and #35

Running snap info obs-studio shows:

name:      obs-studio
summary:   Free and open source software for live streaming and screen recording
publisher: Snapcrafters
store-url: https://snapcraft.io/obs-studio
contact:   https://github.com/snapcrafters/obs-studio/issues
license:   GPL-2.0
description: |
  OBS Studio is software designed for capturing, compositing, encoding, recording, and streaming
  video content, efficiently. _This is a community-supported modified build of OBS Studio; please
  file issues on the Snapcrafters GitHub:_ https://github.com/snapcrafters/obs-studio/issues
  
  **Batteries included**
  
  The snap of OBS studio comes pre-loaded with some extra features:
  
    * Supports **nvenc (NVIDIA) and VA-API (AMD & Intel) accelerated video encoding**.
    * **Advanced Scene Switcher** plugin; an automated scene switcher
    * **Browser** plugin; CEF-based OBS Studio browser plugin
    * **Directory Watch Media** plugin; filter you can add to a media source to load the oldest
    or newest file in a directory.
    * **Dynamic Delay** plugin; filter for dynamic delaying a video source.
    * **Freeze Filter** plugin; freeze a source using a filter.
    * **gPhoto** plugin; connect DSLR cameras with obs-studio via gPhoto.
    * **GStreamer** plugins; feed GStreamer launch pipelines into OBS Studio and use GStreamer
    encoder elements.
    * **Move Transition** plugin; move sources to a new position during a scene transition.
    * **NDI** plugin; Network A/V via NewTek's NDI.
    * **NvFBC** plugin; screen capture via NVIDIA FBC API. Requires NvFBC patches for Nvidia
    drivers for consumer-grade GPUs.
    * **RGB Levels** plugin; simple filter to adjust RGB levels.
    * **Source Switcher** plugin; to switch between a list of sources.
    * **Spectralizer** plugin; audio visualization using fftw.
    * **StreamFX** plugin; collection modern effects filters and transitions.
    * **Text Pango** plugin; Provides a text source rendered using Pango with multi-language
    support, emoji support, vertical rendering and RTL support.
    * **Transition Matrix** plugin; customize Any -> One or One -> One scene transitions.
    * **VNC Source** plugin; VNC viewer that works as a source.
    * **Websockets** plugin; remote-control OBS Studio through WebSockets.
  
  **Connecting Interfaces**
  
  For the best experience, you'll want to connect the following interfaces.
  
     sudo snap connect obs-studio:alsa
     sudo snap connect obs-studio:audio-record
     sudo snap connect obs-studio:avahi-control
     sudo snap connect obs-studio:camera
     sudo snap connect obs-studio:jack1
     sudo snap connect obs-studio:kernel-module-observe
  
  **NDI**
  
  If you want to use the NDI plugin you'll need to connect the Avahi Control interface.
  
     snap connect obs-studio:avahi-control
  
  **Virtual Camera**
  
  Starting with OBS 26.1.0, Virtual Camera support is integrated. Here's how to install and
  configure `v4l2loopback`:
  
     sudo snap connect obs-studio:kernel-module-observe
     sudo apt -y install v4l2loopback-dkms v4l2loopback-utils
     echo "options v4l2loopback devices=1 video_nr=13 card_label='OBS Virtual Camera'   
     exclusive_caps=1" | sudo tee /etc/modprobe.d/v4l2loopback.conf
     echo "v4l2loopback" | sudo tee /etc/modules-load.d/v4l2loopback.conf
     sudo modprobe -r v4l2loopback
     sudo modprobe v4l2loopback devices=1 video_nr=13 card_label='OBS Virtual Camera'
     exclusive_caps=1
  
  **NOTE!** Using `video_nr` greater than 64 will not work.
  
  **Removable Storage**
  
  To access content on external storage, connect to the removable-media plug:
  
     snap connect obs-studio:removable-media
  
  **gPhoto**
  
  The gPhoto plugin allows some DSLR cameras to be connected via USB. You'll need to connect the
  Raw USB interface.
  
     snap connect obs-studio:raw-usb
  
  **3rd Party plugins**
  
  To install pre-compiled plugins, download and extract the plugin to
  `~/snap/obs-studio/current/.config/obs-studio/plugins/`.
  
  This is how the Input Overlay plugin looks when correctly installed:
  
     /home/username/snap/obs-studio/current/.config/obs-studio/plugins/
     └── input-overlay
         ├── bin
         │   └── 64bit
         │       └── input-overlay.so
         └── data
             └── locale
                 ├── de-DE.ini
                 ├── en-US.ini
                 └── ru-RU.ini
  
  If you want to use the Input Overlay plugin, you'll also need to connect the joystick
  interface:
  
     snap connect obs-studio:joystick
commands:
  - obs-studio.eglinfo
  - obs-studio.ffmpeg
  - obs-studio.ffplay
  - obs-studio.ffprobe
  - obs-studio.glxinfo
  - obs-studio
  - obs-studio.srt-ffplay
  - obs-studio.srt-file-transmit
  - obs-studio.srt-live-transmit
  - obs-studio.srt-tunnel
  - obs-studio.vainfo
  - obs-studio.vdpauinfo
  - obs-studio.vulkaninfo
snap-id:      6uLU2MJmBURfLNz4rmL4WT2CmtVULE2u
tracking:     latest/stable
refresh-date: 2022-02-08
channels:
  latest/stable:    27.1.3 2021-12-20 (1284) 418MB -
  latest/candidate: ↑                              
  latest/beta:      ↑                              
  latest/edge:      27.2.1 2022-02-24 (1287) 439MB -
installed:          27.1.3            (1284) 418MB -

Of particular interest is:

  **3rd Party plugins**
  
  To install pre-compiled plugins, download and extract the plugin to
  `~/snap/obs-studio/current/.config/obs-studio/plugins/`.
  
  This is how the Input Overlay plugin looks when correctly installed:
  
     /home/username/snap/obs-studio/current/.config/obs-studio/plugins/
     └── input-overlay
         ├── bin
         │   └── 64bit
         │       └── input-overlay.so
         └── data
             └── locale
                 ├── de-DE.ini
                 ├── en-US.ini
                 └── ru-RU.ini

I've extracted the .so file to either:

$ find /home/$USER/snap/obs-studio/current/.config/obs-studio/plugins
/home/opyate/snap/obs-studio/current/.config/obs-studio/plugins
/home/opyate/snap/obs-studio/current/.config/obs-studio/plugins/shaderfilter-plus
/home/opyate/snap/obs-studio/current/.config/obs-studio/plugins/shaderfilter-plus/bin
/home/opyate/snap/obs-studio/current/.config/obs-studio/plugins/shaderfilter-plus/bin/64bit
/home/opyate/snap/obs-studio/current/.config/obs-studio/plugins/shaderfilter-plus/bin/64bit/libobs_shaderfilter_plus_linux_x64.so

And:

$ find /home/$USER/snap/obs-studio/current/.config/obs-studio/plugins/
/home/opyate/snap/obs-studio/current/.config/obs-studio/plugins/
/home/opyate/snap/obs-studio/current/.config/obs-studio/plugins/libobs_shaderfilter_plus_linux_x64.so

...but in neither location does ShaderFilter Plus show up in my effects options.