Put everything from the rhubarb down to the orange juice in a large pot. Cover and bring to a boil; then remove the cover and reduce to a gentle simmer for 10 to 15 minutes, until the rhubarb pieces are soft. Stir frequently and deeply, to avoid scorching.
Stir in prepared strawberries, bring back to the boil, then turn heat off.
(Optional)If you are using liquid stevia, you can add a bit more if desired, to taste. But don't add sugar at this point, it won't dissolve.
Pack hot into half-litre (US pint) jars.
Leave 3 cm (1 inch) headspace.
Debubble, adjust headspace.
Wipe jar rims.
Put lids on.
Process in a water bath or steam canner.
Process jars for 15 minutes; increase time as needed for your altitude.