I could try using Etcher, as I used Rufus as that was what CoreELEC’s page suggested. I’m not sure the issue is because of a problem writing the image (as the drive went from having an entire 64gb of unallocated space to the 2 partitions described above, which apparently is correct) , but I’ll keep it in mind.
I did remove and insert the card again, but to no avail. It shows only the drive letter of the USB card reader itself when inserted, but none of the partitions on it. Attempting to double click on the drive letter comes up with a “Windows can’t recognize anything, you’ll needs to format it. Do you want to format?” dialog.
Attempting to go to Disk Management shows the following (I have attempted to upload a clipped part of the screenshot), illustrating the drive is there along with the 2 partitions, yet the option to assign a drive letter to the one you suggested is greyed out. Are you sure that Windows10 64-bit can interact with FAT16?
CoreELEC_Issue_install_2020-03-05 152947|690x170
Edit: I managed to finally get to interact with the drive. This required reflashing (this time with Etcher), which, even after removal and replacement of the USB SD card reader, still did not allow browsing - asking again to format the volume. However, this time for some reason, it did let me manually assign a drive letter and browse to the drive.
I’m not sure if the problem is Windows 10 x64, the size of the MicroSD (64gb), an issue with Rufus vs how Etcher flashes etc… but even then having to manually assign a drive letter seems overly complex. I certainly hope things get easier from this point forward. Thank you all.