The official way to obtain Mplus is by purchasing it directly from the Muthén & Muthén website. They offer various versions and pricing options, including a free demo version that can give users a taste of the software's capabilities.
While nostalgia is powerful, using Mplus 6.12 in a contemporary research environment is problematic: Mplus 6.12 Base Program and Combination Add-on setup free
I can point you toward that match your specific project needs. The official way to obtain Mplus is by
Have a legitimate copy of Mplus 6.12 running on Windows 11? Share your compatibility tweaks in the comments below. Mplus 6.12 Base Program and Combination Add-on setup free