Hi, @Percolate
Thanks for posting, and welcome to the Roku Community.
I appreciate you for sharing your inquiry about using the Roku 3 remote with the newest Roku Ultra.
The Roku 3 remote came with a Roku Voice Remote, which is compatible with newer Roku devices, including the Ultra. For best results, it is important to ensure that the Roku 3 remote is in good condition.
Additionally, the newest Roku Ultra comes with the Roku Voice Remote Pro (2nd Edition) with improved features.
I hope you find this information helpful, and let us know if you need further assistance.
Thanks,
The Roku Community Team.
Takashi O.
Roku Community Moderator