Finally got there (I think)
Been trying to bake a sourdough loaf of a decent standard for about a year now.
Starter is 1:1:1 50/50 wholemeal/strong bread flour.
Initially followed 500g strong white with 25g starter fed at 1:2:2 for the levain. Baked on a pizza stone.
Recently moved to tartine recipe and Dutch oven after watching The sourdough journey's videos.
Watched proof bread videos over the weekend and incorporated his mixing/kneading technique after adding the levain to the autolyse.
Last few loaves have used 2ltr measuring jug to BF, accidentally let last night's loaf go to about 35-38% rise instead of the recommended 20-30% of the tartine 
So so chuffed to find a ear, near perfect crumb and decent oven spring (did seem to hold itself better before entering the oven).
Now do it 50 times in a row so that you know it wasn't a fluke. Just kidding!
Very attractive, both inside and out.
Paul
Haha, yeah, that's the next challenge to replicate it every-ish time. I know what I did yesterday though, I take measurements of the temperature all the time to make sure I'm in the ballpark figure. I just need to allow the same % rise in the BF and I will be ok (I think haha)
I am so pleased with it.
That looks like a great loaf. Congratulations! It's a great feeling when you get the first loaf that is like you wanted it to be. Enjoy!
Honestly, it's been so long getting not quite there. Incremental progress but today it all came together.
So chuffed ☺️
Going by your description, you’ve made some good progress with your lifting and form. The increase of 35-38% instead of the recommended 20-30% might be because you didn’t activate the gluten enough, or maybe the starter was stronger than expected.
That looks excellent! Well done.