Can't access onedrive in another tenant

I want to create an aplication that will access and read all data from onedrive in another tenant.
The app will act like a daemon in backgroud, without any user intervention. I want to use MIcrosfot Graph API to access data in onedrive.

Naming convention:
X - my tenant, where my application is registered
Y - some other tenant whose onedrive I want to be accessible by my application in my tenant X

I use such scope

And in my python code i use scopes=".defualt" and client msal.ConfidentialClientApplication.
Code for authorization:

client_app_auth = ConfidentialClientApplication(
    client_id=CLIENT_ID,
    client_credential=CLIENT_SECRET,
    authority="https://login.microsoftonline.com/" + TENANT_ID,
)
def save_refresh_token(refresh_token: str):
    with open(REFRESH_TOKEN_PATH, "w", encoding="utf-8") as file:
        file.write(json.dumps({"refresh_token": refresh_token}))
@app.get("/login")
def login():
    url = client_app_auth.get_authorization_request_url(
        scopes=SCOPES,
        redirect_uri="http://localhost:8000/auth/callback",
        prompt="consent",
    )
    return {"login_url": url}
@app.get("/auth/callback")
def auth_callback(code: str):
    result = client_app_auth.acquire_token_by_authorization_code(
        code,
        scopes=SCOPES,
        redirect_uri="http://localhost:8000/auth/callback",
    )
    if "access_token" in result:
        save_refresh_token(result["refresh_token"])
        return {"message": "Authentication successful", "results": result}
    else:
        return {"message": "Authentication failed", "details": result.get("error")}

Code for listing all users drives:

@app.get("/listdrive")
async def get_all_drive():
    with open(REFRESH_TOKEN_PATH, "r", encoding="utf-8") as file:
        refresh_token = json.load(file)["refresh_token"]
    auth_token = client_app_auth.acquire_token_by_refresh_token(
        refresh_token=refresh_token, scopes=SCOPES
    )
    if "access_token" in auth_token:
        save_refresh_token(auth_token["refresh_token"])
        access_token = auth_token["access_token"]
        graph_endpoint = "https://graph.microsoft.com/v1.0/users/" + USER_ID + "/drive"
        headers = {
            "Authorization": f"Bearer {access_token}",
            "Content-Type": "application/json",
        }
        user_response = requests.get(graph_endpoint, headers=headers)
        user_data = user_response.json()
        return user_data

This is configuration of authenticatoin in tenant X:

Program works fine when I login with my tenant X acccount (also global admin). I'm able to list drives and then use driveId to list files in it.
BUT, when i try to login with Y account i get such error:

I'm trying to login with Global Admin account from tenant Y, so I dont undertstand why would i need some admin approval if I AM the admin.
I've added account from tenant Y to tenant X as a Guest/ExternalAzureAD.

Could somebody help me undestand where I'm making the mistake and how to fix it?

Or maybe I'm approching my endgoal from wrong angle altogether?