The most important change has to do with WebUI. It affects users that haven't set their own credentials and are use the default ones. Those will not be accepted now and qBittorrent will generate a random password and output it in the console for you to use. Then you can login and configure a password.
输入systemctl status qbittorrent
日志里会有随机密码
The WebUI administrator username is: admin
The WebUI administrator password was not set. A temporary password is provided for this session: 随机密码
You should set your own password in program preferences