Some features were recently uploaded but they were developed some time ago, it's been a few months since I stopped messing for real with Steem. For the moment there's nothing more I want to do with it. Currently, the v4.2 beta doesn't offer any real emulation improvements, only features. That would be the first time for a major release...
Emulation improvements are different from features, they're far more interesting. For example, adding native support for STX disk images was interesting because there were some emulation issues to solve, but those improvements are already in v4.1.2. The Control Panel was still fun because it's a hybrid feature. DirectMusic and TCP/IP were frankly boring (probably buggy as hell too).
So until I find something fun to do or get new ideas or new emulation insights, there will be a little pause in development. Release date of v4.2 is undetermined (features must be tested).
There will be a little emulation improvement after all:

That monochrome demo removes the lower border
New Development Activity

Someone asked whether a RetroArch core was a possibility for Steem SSE. After some investigations I like the idea very much and if possible it will become reality, at least in Windows.
Here's the first "proof of concept" picture:
Awesome! Do you have plans to try and get Netplay working with the core?
If I got it right, Netplay can work with cores that implement serialization, which should be the case of Steem SSE, but performance could be a big issue.
I have no insight in these kind of things, but I can imagine it being a challenge. But I am just going to cross my fingers. Netplay would be great to have. Especially since it's not working with the Hatari core...
Serialization is a technical word for loading/saving memory snapshots, it's no big challenge. The challenges are putting it all together, and finding time for it.
Ah so it's basically sending the snapshots data between the connected emulators, or at least the bits that have changed? So that would require a lot of optimization I assume?
Full snapshots AFAIK.
I get my knowledge from their site:
First beta available:
https://sourceforge.net/projects/steemsse/files/Steem%20SSE%20Beta/Steem64_libretro_R6.7z/download
There's still much to do for the libretro core and it hasn't progressed much.
Normally Steem SSE 4.2 should be released in a few weeks, bugs or not, emulation improvements or not, and the core will remain beta for a while.
Update:
Just released a 4.1.2 version with a few fixes.
v4.2 still planned "soon" but there are some problems to check in MIDI emulation.
RetroArch, I don't know yet, sorry about that.