“There are a lot of older Kindles out there that don’t do much of anything else besides being used to download and read books.”
Those are the best ones. Anything else is a pile of trash. I have the first color Kindle (got it for $50 about a year after it came out). It was kludgy at best.
I got one of those Fire HDMI sticks when they were available for $20 for Prime users ... Another pile of garbage. The remote died after six months (tried every resync and voodoo ritual there was ... Even opened it up to look for broken traces or solder issues). I can’t buy another one unless I spend $30 on the one that has a microphone I will never use.
I like Amazon/Amazon Prime content, but their hardware sucks and their bastardized version of Android is an atrocity.
For reading books, I prefer the plain Kindle Paperwhite.