I know this device is no longer supported, that it is probably slow, etc... but can it install and run apps? Can it receive miracast video from a phone? Etc.. what works and what does not work today? Thanks!
I believe you'll find very little that still works with any level of satisfaction. I dropped my 3100s (Roku 2 XS) into a drawer years ago because its performance had dropped to the point that YouTube was unusable. And many of the more recent channels (Disney+, HBO MAX as examples) simply won't work on it at all. Considering you're talking about a device that is more than 10 years old, it's not unexpected to have issues with newer product.
Yes, I would expect it will still get whatever the last update Roku made available for it, and any channels that aren't specifically blacklisted for that device will probably still get channel updates. But odds are they won't work well.
I'm hoping it will allow video cast from one of the Android Play Store apps (with a corresponding Roku app, either downloaded directly or side-loaded). If that works, it's probably the only Roku app I'll need.
In general Roku devices are not a valid target for casting from apps. YouTube is one exception. I do know there are Android apps that do permit screen sharing to a Roku, but that's not the same as casting. But will it work on a Roku player as old as yours? I have no idea. I had an Android phone back in 2017, and I could screen share to a Roku TV and Ultra player. But both of those devices are far, far newer and more powerful than your 3050.
I also have a Roku 3. I cast to it from my Pixel 6a using the Web Video Caster app from the Play Store. There is a corresponding Roku app which handles the server side and plays the video. Using that app I can cast pretty much any non-DRM-protected video that I can play in a browser.
I recently came across the Roku 2 3050R and would like to use it on another TV. Once I get a chance to try it I'll try to come back here and report the results.
There are two versions of the Roku 3, and currently they are both still supported, so they get the latest OS updates. My guess is you will still be able to screen share from your Android phone, but don't expect performance on the Roku to be very good. Might not be an issue is you simply cast what's playing and let it run. But any interaction (pausing the video for example) that comes from the Roku might be laggy.
Ok I have the Roku 2 3050R. A few things I've determined:
1) The Web Video Caster app works well between my Pixel 6a and the Roku, as long as I check the box to route the stream through my phone. Based on early testing, it works just fine for YouTube videos and other non-DRM videos. That's my primary use case for the device. But I cannot cast Amazon Prime videos, and presumably other DRM videos. Responsiveness is OK (but not snappy) on the WVC.
2) The YouTube Roku app is intolerably slow.
3) The Android Roku remote app works just fine. Also the 3050 IR remote works with my other Rokus, and the IR remote from the other devices work on the 3050.
4) The Amazon Prime Roku app will not run on this device.
5) I have multiple Rokus in my house. I've created a separate Roku account for this device so that I can delete the non-working apps on this device while keeping all the apps on my other devices. For now I just have the Roku app (which I don't use) and the WVC app.