The ATF has published its Final Rule on pistol braces to the Federal Register, thus starting the 120-day clock to register your brace-equipped firearm or modify the firearm to comply with GCA/NFA regulations.
You can see the published rule here:
If you've missed all this, you can get up to speed with this post:
The end of the 120-day window is May 31st, 2023. Which way, western man?