There is a desert called Panacotta that disolves unflavorwed gelatine into hot milk, with vanilla, and normally, sugar to create a starch-free custard. You could adapt this to your tap;ioca, adding the unflavored gelatin to you tapioca recipe. Another option is to use One of the sugar alcohols, as they mimic sugar in texture. Erythritol is generally considered the best if these, as it has no calories, and does not raise blood sugar levels. Also, it doesn't cause the gastric problems associated with some of the other sugar alcohols. On brand is = https://www.amazon.com/dp/B004X71550...41c16a1d8ad503
Good luck in your quest for great tapioca pudding. It brings back fond memories of eating at my grandparent's home when I was a child.
Seeeeya; Chief Longwind of the North