Manifest is not valid JSON. Line: 21, column: 1, Syntax error. Could not load manifest.?

Question

{
    "name": "Extension",
    "version": "2.0.0",
    "manifest_version": 4,
    "description": "This is a Test.",
    "homepage_url": "https://example.com",
    "icons": {
        "16": "icons/16.png",
        "48": "icons/48.png",
        "128": "icons/128.png"
    },
    "options_page": "src/options/options.html",
    "background": {
        "scripts": ["src/test0/test1.js", "test2.js", "main_compiled.js"],
        "matches": [""],
        "js": ["bubble_compiled.js"],
        "css": ["bubble_gss.css"],
        "all_frames": true
    }

Answer 1

You need one more bracket to "close" your json at the end.

{
    "name": "Extension",
    "version": "2.0.0",
    "manifest_version": 4,
    "description": "This is a Test.",
    "homepage_url": "https://example.com",
    "icons": {
        "16": "icons/16.png",
        "48": "icons/48.png",
        "128": "icons/128.png"
    },
    "options_page": "src/options/options.html",
    "background": {
        "scripts": ["src/test0/test1.js", "test2.js", "main_compiled.js"],
        "matches": [""],
        "js": ["bubble_compiled.js"],
        "css": ["bubble_gss.css"],
        "all_frames": true
    }
}