Recently, not quite sure since when, Thumbnails in Nautilus stopped being displayed as usual, most likely due to an update?

I have done this:

sudo apt install ffmpegthumbnailer
And this:

Press Ctrl+H, enter into the folder named .cache. Then enter in the folder thumbnails. Delete everything in there. Restart your PC.
Thumbnails for videos are back, but my local mp3 music files are still not showing thumbnails for album art which I have added manually over time using Ear Tag.

Is there anything else I can try?