I noticed yesterday that there are some fires involved in this change. However, they are all under the name "kindle fire" rather than "Amazon fire". The kindle part of the name was changed to Amazon in 2013. Only the earliest fires, up to at least one of the HDX line (2 sizes were offered, 7" and 9").
As in the case of kindle, NONE of these devices offered replaceable batteries. The hardware is so old that virtually no newer apps/games will work on them and 90% of the software that will work on them is no longer offered or even compatible with newer devices.
Also, they are very limited (I'm not sure any of them even offer micro-SD cards) and are incredibly slow to boot.
Most people who still have them only keep them for the one or two games that won't work on newer models. That's not unique to these old dinosaurs. I have one game that will only work on ONE of my devices (out of 7), and that device is generation 9 (2019 release).
Like the kindles, you're probably better off taking Amazon's offer for gift card and discount on a new device. Get something for these dinosaurs before they are fossils.
Just a note -- I'm getting my information from the posts of the email sent by Amazon on the Amazon Digital and Devices forum. None of my devices are nearly old enough to qualify for anything like this.