What is the mobile messenger for communication by interests?

Question

Google Workspace

Hello. Tell me if there is a mobile messenger like whatsapp, viber, kakaotolk, where you could create your own interest group, for example, AUDI A4 2011. It is necessary that all owners of this car can get into this group.
Not only those that I have in my notebook, but for example, a person completely unfamiliar to me could find this group in the application menu and add it, and I would receive a push notification that someone was added.
There is an idea to make such a messenger. It will differ from the existing ones precisely in that people will be able to find interest groups in it.
For example, you need to sell a cell phone, you select the group Electronics - Purchase of cell phones - create a new topic (I will sell an iPhone 5c). At the same time, you see that in this group there are, for example, 50 people from your city, these can be buyers of cell phones, and by creating a new topic in this group, you are sure that all these interested 50 people will see this topic, since they are subscribed to this group and they will receive a push notification. In the created topic, interested people will already unsubscribe to you.
At the same time, the messenger will have all the standard functionality like WhatsApp. It will be possible to leave with the person who unsubscribed to you in the topic in a private chat, send him a photo, etc. Make the interface as simple and intuitive as possible.
I would like to hear opinions on this idea.

Answer 1

I bought it!

Answer 2

That is, you want to shove a regular forum into a smartphone and call it a messenger? :)