Installation instructions about onlyoffice.github.io

[rmeissn]

Just for completeness (Flatpak installation):

1. Navigate to <user-home-dir>/.var/app/org.onlyoffice.desktopeditors/data/onlyoffice/desktopeditors/sdkjs-plugins and create a folder which is named after the guid hash inside config.json (including the "{}") - so {7CDB02C9-A0BF-4B56-9A1A-71C860B8498F}
2. Open the created folder
3. Download this repository (optionally the develop branch) as a zip file to the previously created folder and extract the zip file there
4. Make sure that the guid named folder contains everything as shown here - move files if the unzip process created only one folder, named after the zip file
5. OPTIONAL: edit "scripts/langTool.js" to use a local instance of LanguageTool by replacing all 2 occurrences of https://languagetool.org/api/ with e.g. http://localhost:8081/
6. Restart OnlyOffice and look for the plugin at the plugins tab

[rmeissn]

Never mind, I've named the folder in the wrong way - forgot the "{}" around the hash.
It works now.

[ShockwaveNN]

Could you attach plugin file?

Maybe this will help

https://api.onlyoffice.com/plugin/faq