If your Fire TV Stick is running a newer software version, this method may not work for you.
The firmware downgrade drill for the Samsung Galaxy devices is not much complicated as compared to the phones manufactured by other brands.
It requires you to boot the device first into Download/Odin Mode, and then into Android Recovery Mode.
I assume that you have already done as described above, so let’s go ahead.
If this tutorial worked for you (and it should work), please leave a comment below and do not forget to mention your phone model and the OS version from and to which you downgraded.
For a list of devices not working with DD-WRT please see wiki page Known incompatible devices.