Thank you for this detailed response. I was able to buy a USB-stick-style SD/mSD reader/writer and a couple of 128gb cards to go with it. I have ubuntu up and running now and a backup as well. I tried following this guide but I keep running into issues around the docker compose part. I think I am in over my head at this point and will just make a local setup the way I know how and try again in the future.
Thanks for the tips about saving my bacon with multiple SD cards.