@ngoering-
Here's a place to check the status of Roku models:
https://developer.roku.com/docs/specs/hardware.md
The 3600 is still listed as updatable.
My 3600X updated to 12.5 several days ago. In fact, it's the only one of my Rokus to receive it so far.
Roku Community Streaming Expert
I am not a Roku employee, only a user like you. Please, no support questions via private message -- post them publicly to the Community where others may benefit as well.
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Ultra 4800 | Streaming Stick 4K+ 3821 | TCL Roku TV 43S245/C107X