browser.config.ts

    maxInstances: 10,

    maxInstancesPerCapability: 1,
    //
    // If you have trouble getting all important capabilities together, check out the
    // Sauce Labs platform configurator - a great tool to configure your capabilities:
    // https://docs.saucelabs.com/reference/platforms-configurator
    //
    capabilities: [{
        // maxInstances can get overwritten per capability. So if you have an in-house Selenium
        // grid with only 5 firefox instances available you can make sure that not more than
        // 5 instances get started at a time.
        maxInstances: 5,
        //
        browserName: 'chrome',
        'goog:chromeOptions': {
            args: [
                '--no-sandbox',
                '--disable-gpu',
                '--start-fullscreen',
                '--disable-infobars',
                '--disable-notifications',
                '--window-size=1366,2160'
            ],
            prefs: {
                'directory_upgrade': true,
                'prompt_for_download': false,
            }
        },
    },
    {
        maxInstances: 5,
        browserName: 'firefox',
        'moz:firefoxOptions': {
            args: [
                '--window-size=1366,2160'
            ],
        },
        'acceptInsecureCerts': true,
    }],

tsconfig.json

{
    "compilerOptions": {
        "lib": [
            "ES2020"
        ],
        "types": [
            "node",
            "webdriverio/async",
            "@wdio/mocha-framework",
            "expect-webdriverio"
        ],
        "moduleResolution": "node",
        "target": "es2019",
        "module": "commonjs",
        "baseUrl": ".",
        "noImplicitReturns": true,
        "resolveJsonModule": true,
        "esModuleInterop": true,
        "noUnusedLocals": true,
        "noUnusedParameters": true,
        "outDir": "./dist",
        "pretty": true,
        "noImplicitThis": true,
        "strict": true
    },
    "exclude": [
        "./node_modules"
    ],
    "include": [
        "./*.ts",
        "./test/**/*.ts",
    ],
    "compileOnSave": true
}

wdio.conf.ts

autoCompileOpts: {
        autoCompile: true,
        // see https://github.com/TypeStrong/ts-node#cli-and-programmatic-options
        // for all available options
        tsNodeOpts: {
            transpileOnly: true,
            project: 'tsconfig.json'
        },
    }