Combine 1 pint blueberries, 1/2 cup sugar and lemon juice in a bowl. Toss to combine. Cover and refrigerate. Stir every 30 minutes for 2 hours.
In a 2 quart saucepan over medium heat, heat rhubarb, 1/4 cup sugar, strawberry jelly cinnamon, salt and nutmeg until boiling. Reduce heat to low; cover and simmer 10 minutes, stirring often, until rhubarb is tender. Let cool to room temperature, then cover and refrigerate.
In a medium mixing bowl, beat the sugar into the eggs until thickened and pale yellow. Beat in the flour and salt.
Bring the milk to a simmer in a heavy medium saucepan. Slowly beat the hot milk into the eggs and sugar. Pour the entire mixture back inot the pan and place over low heat. Stir constantly with a whisk or wooden spoon until the custard thickens slightly. Be careful not to let the mxiture boil or the eggs will scramble. Remove from the heat and pour the hot custard through a strainer into a large, clean bowl. Allow the custard to cool slightly, then stir in the cream and vanilla. Cover and refrigerate until cold, or overnight.
When all three parts are cold then drain the juice from the blueberries and add to the ice cream base. Mash the blueberries until pureed and add to the ice cream base. Add the stewed rhubarb to the ice cream mixture.
Make sure the ice cream mixture is mixed well. Then freeze in your ice cream machine (the number of batches required will depend on the size of your machine) according to the manufacturer's instructions. If you like a firmer ice cream then transfer to a freezer safe container after the machine is done and freeze at least 2 hours.