Here's the Python code

import httpx

url = "https://www.steamgifts.com/"
headers = {
    "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:147.0) Gecko/20100101 Firefox/147.0",
    "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",
    "Accept-Language": "zh-CN,zh;q=0.9,zh-TW;q=0.8,zh-HK;q=0.7,en-US;q=0.6,en;q=0.5",
    "Accept-Encoding": "gzip, deflate, br, zstd",
    "DNT": "1",
    "Sec-GPC": "1",
    "Connection": "keep-alive",
    "Upgrade-Insecure-Requests": "1",
    "Sec-Fetch-Dest": "document",
    "Sec-Fetch-Mode": "navigate",
    "Host": "www.steamgifts.com",
    "Sec-Fetch-Site": "none",
    "Priority": "u=0, i",
    "Sec-Fetch-User": "?1",
    "TE": "trailers",
}
client = httpx.Client(http2=True, cookies=cookie_io.load())
response = client.get(url, headers=headers)
print(f"Responnse code: {response.status_code}")

I copied request headers and cookies from my Firefox Browser into my Python code, and use HTTP/2.

Why SteamGifts return 403 response?