Chrome extension not changing headers is http but works in https (manifest v3)

Question

i am working on a chrome extension that changes headers (adds custom Accept-Language header) and connects to pre-specified proxies. I was testing my product and found out that when i add some custom headers, they are only sent/changed if i use http. I created a php page that displays recieved headers.

When i visit https://mytestes.com I get this

accept-language: hu
proxy-switching-extension: true

But when using http:////mytestes.com i get this, where the custom header is not even added and the Accept-Language header is not changed (the headers match my chrome network tab)

accept-language: sk-SK,sk;q=0.9,cs;q=0.8,en-US;q=0.7,en;q=0.6
proxy-switching-extension: --> **NOT SENT**

My manifest look like this

{
    "name": "HTTP headers manipulator 1.0",
    "version": "1.0",
    "description": "Extension allows user to add custom headers to the requests sent from the web browser",
    "permissions": [
        "storage",
        "tabs",
        "webRequest",
        "declarativeNetRequest", 
        "declarativeNetRequestWithHostAccess", 
        "declarativeNetRequestFeedback",
        "proxy"
    ],
    "declarative_net_request": {
        "rule_resources": [
          {
            "id": "ruleset_1",
            "enabled": true,
            "path": "rules.json"
          }
        ]
      },
    "background": {
        "service_worker": "background.js"
    },
    "host_permissions": [
        "https://*/*"
    ],
    "content_scripts": [
        {
            "matches": [
                "https://*/*",
                "http://*/*"
            ],
            "js": [
                "contentScript.js"
            ]
        }
    ],
    "manifest_version": 3
}

rules.json

[
  {
    "id" : 1,
    "priority": 1,
    "action": {
      "type": "modifyHeaders",
      "requestHeaders": [
        { "header": "Proxy-switching-extension", "operation": "set", "value": "true" }
      ]
    },
    "condition" : {
      "urlFilter" : "|http*",
      "resourceTypes" : ["script", "main_frame", "sub_frame"]
    }
  }
]

background.js

chrome.declarativeNetRequest.updateDynamicRules({
    addRules: [
        {
            id: 1,
            priority: 1,
            action: {
                type: 'modifyHeaders',
                requestHeaders: [
                    {
                        header: "Accept-language",
                        operation: 'set',
                        value: "hu"
                    },
                ],
            },
            condition: {
                urlFilter: '|http*',
                resourceTypes: [
                    'main_frame',
                    'sub_frame',
                    'script'
                ],
            },
        },
    ],
    removeRuleIds: [1]
}, async (result) => {
    console.log('created', result);
});

I tried changing the condition values, but without any luck, could you please help me with this ? I need to use http for http proxies and am unable to change headers in http currenlty :( Thank you :)