OK, I've got some further information to share about the Amazon Kindle devices.
This shows the list of all current and legacy Amazon Fire tablets. By "legacy", Amazon describes them as 'retired', which I take to mean that they no longer make or directly sell them (there may be other sellers of new/used versions of these devices on Amazon).
The Current devices are of course supported for Terraria and should be able to get the update, if they haven't already gotten it.
For the Legacy devices, I've highlighted the models and status:
View attachment 118154
- The Green columns are the 3rd gen and later models, they should already have the update.
- The Yellow columns are the 2nd gen HD models - they SHOULD be able to get the update. If you have one of these models and still cannot get the update within 24 hours, please let me know.
- The Pink column is the 2nd gen non-HD model*, and the 1st gen model - these are not supported, and will not get the update.
*The issue with the 2nd gen non-HD model is that it does not have Bluetooth support. Bluetooth is required to support external controllers.
The issue with the 1st gen Kindle Fire was already noted - insufficient RAM and lack of OS support.
I've asked about this model, awaiting an answer. The specs I find for this device include Bluetooth, so I'm not sure what the issue is.