I have successfully liberated/degoogled my mobile (CrDroid) , watch (AoS), Kindle, FireTvStick, router and laptop. Though I don’t seem to find anything on Alexa / Echo Dot.
The best I could do was adding a blocklist on my Pihole, though didn’t seem to do much. I disabled all ad related settings in the mobile companion app.
Yes I could host an homeassistant or Mycroft on a Raspberry Pi, but the alexa speakers are too good a product for listening to music (For me).