Microsoft took a few months to release the first Windows 10 19H1 build to the Slow Ring, with build 18342.2 only making its way to that group of Insiders a couple of weeks ago. Now, however, it looks like the company is back on track with its update schedule, and build 18351 is now available for Insiders in the Slow Ring.
There were a few build releases in the Fast Ring between 18342 and 18351, but most of the changes revolve around fixing bugs, since we're nearing the public release of Windows 10 19H1. The only major addition is Emoji 12.0, which was finalized by Unicode in February and added to Windows 10 with build 18348. New emoji added with this update will now be linked to certain words so that they're automatically recommended.
Aside from that, a few bugs have been fixed, and you can check out which fixes were made in build 18346 and 18351 when they were released to the Fast Ring. The Slow Ring release is actually build 18351.7, and it includes an additional fix for Chinese versions of games not working.
As we near the release of Windows 10 19H1, or version 1903, the majority of builds will mostly focus on fixing any issues in the update. Version 1809 was a troublesome one for Microsoft and Windows users, so hopefully, a similar situation can be avoided this time around.