I was using a firestick 4k up until a few weeks ago before they updated the firmware and broke Kodi audio pass through.
Now I use a mini PC with Windows 10. Kodi v19 Matrix beta 2 with the updated PlexKodiConnect add-on. I have a Harmony hub remote that runs Kodi perfectly. I have no issues at this point. It was nice to use a $25 device for a couple years but this new setup, although more expensive, is better, especially with the new Kodi version. 4K movie rips with HDR works perfect without any modifications. 4K video just looks smoother. Also, for audio, I don't have to change any settings to switch between stereo and multichannel which was a bit cumbersome on the firestick. The only thing I use the firestick for now is ChannelsDVR, which works well, but is far from state of the art video or audio but it offers the ability to watch TV without commercials which is a must, and is inexpensive, unlike cable tv.