Notomato sauce.

Could you mix a small bit of tomato puree with stock and maybe add some chopped aubergine and/or mushrooms?

I can't really think of anything that truly replaces tomatoes in a spag bol.

You could try a white bolognese sauce - culinaryginger.com/traditional-white-bolognese-sauce/

Can’t you get your acid reflux sorted out?

There’s a magic pill called Omazaprole, have you asked your GP?

How about using red peppers? You could roast them first with olive oil to bring out the flavour, then blitz them to make a purée.
I thinks I’d cook the mince and other ingredients first and then add the purée at the end, so not to spoil it’s flavour.

Yes, as ferry23 suggests, a white Bolognaise sauce with meat, onions, garlic, carrots, celery, white wine and a good stock would be an alternative. Known as Ragu Bianco.
You could add milk or cream according to some recipes. I wouldn't but that is a matter of preference.

I’m not sure any of these would help with acid reflux, you need to cut out more than tomatoes

A green pesto? Basil, olive oil, pine nuts and grated Parmesan with a dash of lemon.
Rocket or one of the spicy ‘Asian greens’ works too. Or spinach with a dash of chilli.

You’re absolutely right Aggie but cutting out tomatoes is the hardest change for me.

Oreo, I did have the reflux pretty much under control but have had to come off Lansoprazole due to side effects There are other meds but my GP doesn’t want to prescribe them until the tests for yet another condition have been carried out. Such is old age!

I will try the white bolognese sauce though definitely without cream.

You can buy acid free tomatoes, if you can source them. Then you can make your own. I once tried the nomato sauce from the Acid Reflux diet. It was actually quite good.