Can I use fire tablets or just general cheap tablets for an Alexa Replacment

I would love to replace Alexa and use the Assist local feature. I have a subscription and was wondering if I could just use tablets like Alexa, except for Assist. Maybe an external Bluetooth speaker for control. Do devices exist that look like Echo 8’s but just have the Android OS where I could download the companion app and use assist plus Open AI? The companion apps could even use these devices to transmit Bluetooth.