In case someone has properly configured their Anki Connect and runs into this issue later on, you can add this to your config in Anki:
"Referrer-Policy": "origin",
So, your whole Config for AnkiConnect would look like:
{
"Referrer-Policy": "origin",
"apiKey": null,
"apiLogPath": null,
"ignoreOriginList": [],
"webBindAddress": "127.0.0.1",
"webBindPort": 8765,
"webCorsOrigin": "http://localhost",
"webCorsOriginList": [
"http://localhost",
"app://obsidian.md"
]
}