One more option I forgot, and this is embarrassing because it’s actually the one we now use at our house, is to run smartthings initially in a “hub optional“ configuration.
You don’t need a smartthings compatible hub unless you want to use zwave or zigbee devices connected directly to that hub. But there are many devices, typically Wi-Fi but some other protocols as well, which communicate with smartthings “cloud to cloud.“ This is actually how echo devices work with smartthings.
You can use the free Samsung smartthings app without needing to have a hub. You get access to all the same automation capabilities. (And, unfortunately, do suffer many of the same instabilities, although not all.)
There are lots of devices that integrate with both Alexa and smartthings.
So again, if your goal is just to learn more about using advanced Automations, you could do that without getting the hub right away. And you may find that some of the devices you already have have manufacturer-provided smartthings integrations already.
You do have to remember the first rule of home automation: “the model number matters.“ For example, you can download the smartthings app right away, tap the + in the upper right, choose “devices“ and see a list of brands that have smartthings integrations. However, just because you see a brand there doesn’t mean that every model they make has an integration. So you do have to do some additional research. But that might be a very good way to start and just see what you can do between smartthings and Alexa routines. A year ago I would’ve suggested also adding IFTTT, but now that they have gone to a paid subscription model, you might even want to postpone that.
So that’s just another option. I like Meross WiFi devices because they have models which work with homekit, smartthings, and Alexa all at the same time, which gives me a lot of flexibility. And I know that even if my more sophisticated Automations aren’t working because smartthings has a glitch, I will still have basic functionality through the other integrations.
So just one more possibility. Because smartthings is primarily a cloud-based system, the hub is really just a box of radios at present. ( they are promising more local operations in the future, but it’s not here yet.) So if you don’t have devices that need those particular radios, you may not need a hub at all. Choice is good.