Flask会话在移动端浏览器无法保留问题求助

我是Flask新手，从零开发应用学习框架。该应用在桌面浏览器（Edge、Chrome、Firefox）运行正常，但在iPhone 12的Chrome、Safari、Opera、Firefox等移动端浏览器中无法维持会话，始终返回{'status': False}。

后端初始化代码 #

from flask import Flask, jsonify, request, make_response, render_template, session, redirect, url_for

app = Flask(__name__)
app.config['SECRET_KEY'] = "Actual one is a fixed, random string like 89hsfd98sdhf89u983qwj9"

@app.route('/')
def index(): return render_template('index.html')

# This is where the session is created
@app.route('/player/add', methods=['POST'])
def player_add():
     req = request.get_json()
     session['session_key'] = _generate_session_key(STRING_LENGTH)
     session['name'] = req['name']
     return make_response(jsonify({"result": player.player_add(req['name'], session['session_key'])}), 200)


# This is the important one where the session is called
@app.route('/player', methods=['GET'])
def get_session_name():
     try:
          if not _valid_session(): return make_response(jsonify({'status': False}), 200)
          data = player.player_info(session['name'])
     except: data = {'status': False}
     return make_response(jsonify(data), 200)
"""
Many more app routes
"""

if __name__ == '__main__':
    app.run()

前端通信代码 #

fetch(`${window.origin}/player`, {
    method: "GET",
    credentials: "include",
    cache: "no-cache",
    headers: new Headers({
        "content-type": "application/json"
    })
}).then(...)

应用部署在PythonAnywhere上，控制台及后端无报错。我已尝试以下方案但未解决：

• 调用fetch时使用credentials: "same-origin"
• 设置Flask配置：SESSION_TYPE="filesystem"、SESSION_PERMANENT=False、SESSION_COOKIE_SECURE=True、SESSION_COOKIE_SAMESITE='None'
• 使用HTTPS替代HTTP
• 关闭移动端浏览器的“阻止跨站跟踪”功能
• 清理会话并重新生成SECRET_KEY
• 清理浏览器存储的Cookie和历史记录

希望能获得解决该问题的帮助或指导，哪怕是临时的设置方案也可以。

内容的提问来源于stack exchange，提问作者LogicAndTruth