Embedding self-built WebKit framework in Mac app

I'm trying to embed a self-built copy of the WebKit frameworks to a macOS app. Most importantly I hope to get some features to work which Safari offers, but WKWebView in macOS doesn't (getDisplayMedia, Service Workers, WebInspector).

Many years ago I was successful in using a self-built WebKit copy in this Mac app, but it seems the WebKit framework got more complex since them, I guess because of WKWebView's architecture.

That time I had to open the projects for the main frameworks in Xcode, select the framework bundle in the target and change the "Installation Directory" setting to the path @executable_path/../Frameworks. After building WebKit using the build script, I could use otool -L to confirm the changed installation path, which then was displayed for example as @executable_path/../Frameworks/WebCore.framework/Versions/A/WebCore

I tried the same with a current WebKit build:

1. I copied the products for WebKit.framework, WebCore.framework, JavaScriptCore.framework, WebKitLegacy.framework, WebGPU.framework and WebInspectorUI.framework to my app and added it to the "Frameworks, Libraries and Embedded Content" section in the Project's Target/General tab and selected "Embed & Sign" for each framework.
2. In "Build Phases" I made sure that WebCore.framework and WebGPU.framework are only in the "Copy Files" phase (Destination Frameworks) and not in "Link Binary with Libraries", as WebCore is linked through the WebKit umbrella framework and WebGPU gave another error (not sure about how to deal with that framework, as in the system it's in a PrivateFrameworks subfolder).
3. In "Build Settings" I made sure that @executable_path/../Frameworks is entered for "Runpath Search Paths" (it was already probably because of Cocoapods, together with @loader_path/../Frameworks.
4. When I build my app, the system's WebKit version is used. Only when I add the environment variable DYLD_FRAMEWORK_PATH with value @executable_path/../Frameworks in the run scheme, the embedded self-build WebKit frameworks are used.
5. Because of currently necessary backward compatibility my app can use the legacy WebView or WKWebView. The legacy WebView works perfectly with the embedded WebKitLegacy.framework. But if I try to open any URL in WKWebView, no content is rendered and in the console output I can see:

Safe Exam Browser[21391:145678] [Process] 0x10c67d760 - [PID=0] WebProcessProxy::didFinishLaunching: Invalid connection identifier (web process failed to launch)

Safe Exam Browser[21391:145678] [Process] 0x10c67d760 - [PID=0] WebProcessProxy::processDidTerminateOrFailedToLaunch: reason=4

Safe Exam Browser[21391:145678] [ProcessSuspension] 0x10c005040 - [PID=0, throttler=0x10c67d8d8] ProcessThrottler::Activity::invalidate: Ending background activity / 'WebProcess initialization'

Safe Exam Browser[21391:145678] [Process] 0x10c67d760 - [PID=0] WebProcessProxy::shutDown:

Safe Exam Browser[21391:145678] [Process] 0x7fbe89064020 - [pageProxyID=40, webPageID=41, PID=0] WebPageProxy::processDidTerminate: (pid 0), reason 4

2022-02-14 12:53:01.764074+0100 Safe Exam Browser[21391:145678] [Process] 0x10c67d760 - [PID=0] WebProcessProxy::processTerminated:

Safe Exam Browser[21391:145678] [Loading] 0x7fbe89064020 - [pageProxyID=40, webPageID=41, PID=0] WebPageProxy::dispatchProcessDidTerminate: reason=Crash

Safe Exam Browser[21391:146842] [SEBOSXWKWebViewController webViewWebContentProcessDidTerminate:<Safe_Exam_Browser.SEBOSXWKWebView: 0x7fbe88f8b1c0>]

I have the impression that the web process might fail to launch because I didn't embed all necessary parts of the self-built WebKit (the product folder contains a large number of XPC, dylib and .a files). Or some additional paths have to be adjusted before building WebKit, so that the embedded frameworks/libraries are used and not the system provided ones. I also looked at the bundle of the Safari Technology Preview and can see some similarities but also differences.

I would be grateful if anybody could provide me with information how to embed a self-built copy of WebKit into a macOS app. Unfortunately I didn't find any Mac open source browser using an embedded copy of WebKit to get some inspiration from.