So I back it up to a NAS. I bought a Synology NAS (back before they turned into an evil company) which includes a Cloud Sync app which will connect to your Google Drive and sync changes every hour. It's technically sync not backup, but because all deleted files go into a "Trash bin" directory that you can set to never empty, it effectively works as backup for deleted files too (though you can't recover older versions of a file that still exists). The really great feature is that it has the option to sync all files that are in Google Docs/Sheets/Slides format as converted to Word/Excel/PPT. And the great thing about the backup running on your NAS is that it doesn't depend on your computer being on or anything.

I know Synology's considered an evil company now because they seem to tie you to their own hard drives now, but I don't know if there's anything else as easy to set up for reliably syncing consumer cloud files to a NAS. Hopefully there is though, if anyone else knows?

And of course, you can similarly run a backup program on your computer to back up your local files to it, as it's just a network mount.

Storage Box is a little more effort to setup since it doesn't provide an S3 interface and I instead had to use WebDAV, but it's more affordable and has automated snapshots that adds a layer of easy immutability.