I still don’t think you’ll need to replace your V2 hub unless you’ve gotten some reports you haven’t told us about. The V2 actually has more memory than the V3, so it has less trouble with the newest smartthings platform, for what that’s worth. The issue you ran into with all your devices disappearing was one that occurred in the cloud platform, not in the hub itself, as you can tell from the fact that some devices disappeared like your ecobee and your ring doorbell that were never connected to your hub.
I think I’ve already given you this link, but if not, here it is again. This explains what you need to use matter with smartthings. Please read it: it should answer most of your questions.
FAQ: What do I need to add a Matter device to the SmartThings app? Do I need a bridge router device?
Matter Devices communicate one of three ways:
Matter over WiFi
Matter over thread
matter over bridge
The v2, V3, and Station all handle matter over Wi-Fi and matter over bridge the same way.
If you want to use any matter over thread devices, then you have to have a “thread border router.” Many people already have these because they are built into some echo models and some Google nest models. They are also built into the V3 and the station. So the only time you’d have an issue is if you only had your V2, and then you would have to also get some thread border router. Which could either be one of the smart speakers, or could be a smartthings station.
But you don’t need to use thread to use matter. thread is primarily intended to be used with batterypowered matter devices, because Wi-Fi typically has too short of a battery life. But another alternative is to use zigbee batterypowered devices which are connected to a Matter bridge. so no one can say upfront whether you will ever need Thread or not. You would only need thread to communicate with a device that uses thread. It’s up to you whether you ever buy any of those or not.
If you want to stick with an all smartthings setup, that’s up to you. It’s also up to you how many ST hubs you want to have. But if you go that route, you haven’t done anything to protect yourself against the problem that caused you to start this thread in the first place. It could happen again. I’m not saying it will, but since we don’t know why it happened in the first place, we don’t know whether it can happen again. 
Oh, and again, the smartthings station doesn’t have zwave support. The V2 and V3 hubs do. So if you want to use zwave devices, the station by itself is not enough.