In fact, there are quite a few decentralized chat applications, and the one I recommend the most is Wiremin. It can be downloaded and used in China, but there is no Chinese version. The software is also quite simple and not difficult to use.
There is also a software called Session, which has a Chinese version, but many nodes are located abroad, making it hard to connect. Another one is Tox, which is also based on P2P, but it cannot send files in group chats. Those that can send image files should all be using blockchain.
Firstly, decentralized chat software does not require any personal information for registration, but once registered, you must keep your personal ID safe. If you forget it, you will permanently lose your account, and there will be no way to recover it.
The software is based on DHT P2P technology and also uses blockchain technology, completely independent of servers. Even if the official software stops operating, we can still chat normally. The software supports sending images and short videos in normal chats, and the most impressive feature is group chats, which can accommodate tens of thousands of people without issue. It also has a community where the number of participants in group chats seems to be unlimited.
In contrast, WeChat and QQ rarely have groups with tens of thousands of members, which can be inconvenient for some operators. For example, creating a group with hundreds of thousands of people can simplify announcements and chats into one group.
Of course, due to decentralization, there is no regulation, and some inappropriate information in groups cannot be reported. Regular software either shuts down groups or bans accounts, but in the end, you will have to experience it for yourself.