Some of us can't tolerate coffee, whether caff or decaff.
Personally, I would like to drink coffee all day, every day, but it gives me insomnia, heartburn and high blood pressure, so that is a triple no.
Unfortunately there is no substitute that I have ever found that is low in carbs and matches coffee in flavour and general coffee-ness. So I make do with the occasional hot chocolate (cocoa powder, erythritol and double cream), herb teas, sparkling water, sodastream Zeros, and roasted chicory (Prewitts Organic).
The chicory is closest to coffee in colour and flavour. It is caffeine, grain and gluten free, and since it is made from chicory root, which is a plant rather like a parsnip, but has much less starch and a lot more fibre (inulin) which is soluble and prebiotic. I am unsure whether these benefits make it through the roasting process.
Being a plant, when dried and roasted it has quite a lot of carbohydrate, but one or two cups of chicory coffee every morning over the last 18 months have never (to my knowledge, or my Libre screen) ever raised my blood glucose.
https://draxe.com/chicory-root/
I have also tried Teeccino, but found it absurdly expensive and far more phaff than it was worth.