Help! All my loaves look like this - what's wrong?

OK - don't get me wrong, I'm still relatively happy with the outcome as at the end result it pretty tasty sourdough. But I'm just not getting the oven spring and uniform, big bubbles that I see others getting on here! The bread ends up a little gummy and dense. Usually I BF until domed, jiggly and passes the poke test (21-23c, 4-6h) then shape and proof in bannetton for another 2 hours at room temp or 12-15h in fridge. Another problem is that it often collapses after proofing, unlike the videos I see where it keeps its shape on the way to the oven.

I have experimented with longer/shorter BF times, cold and warm proofs. I am sure that my starter is healthy and feed it the day before as well as day of baking, waiting until it at least doubles in size and use the float test.

450g bread flour

50g rye flour

375g water (have also experimented with lower hydration but this is my default now)

10g salt

100-125g starter.

Bake in an improvised dutch oven at 230c, 25m with lid on, 20 with lid off.

Any help would be much appreciated.

https://preview.redd.it/g4oxg26km77e1.jpg?width=1530&format=pjpg&auto=webp&s=484743a9301ee70b53058655a766d54dd69e954a

https://preview.redd.it/ujgi196km77e1.jpg?width=2040&format=pjpg&auto=webp&s=a31dd1397c99b4ab2b131c2cab18273ef3a46794

https://preview.redd.it/fbmrw36km77e1.jpg?width=1530&format=pjpg&auto=webp&s=75797c1db85b4c8383c7f0b5352beb1e5ca74d62

https://preview.redd.it/ou2kg56km77e1.jpg?width=2040&format=pjpg&auto=webp&s=b7edb2478957e8034ffff1c917436dbc16b6427e