Just sent a file. It was converted from a wav to FLAC using SoundConverter in Ubuntu 20.10 in a virtual machine. In Windows, the tags are seen in file explorer, Mp3tag and TagScanner.
I was able to get around by converting the files in windows using FLAC frontend from https://xiph.org/flac/, which strips the tags, then entering the tags using TagScanner. Longer process than I wanted, but seems to work.