Cruciferous vegetables high in fiber have worked for me so far to keep everything regular. I did go get a container of fiber supplement (psyllium husk) and only used it once after realizing it was quite high in carbs.

Getting some dietary fiber from a meal like broccoli and cheese, or my normal breakfast (100 grams chopped kale + 150 gram kale stems + 2 slices bacon + 50 gram egg beater) provides a really nice amount of well rounded low carb calories, keeps the net carbs below 5ish grams and intakes a good enough amount of fiber to...shall we say...keep everything stable. Plus you can put this on the night before and have a good meal ready to hear and eat, once it's sat over night in the fridge it taste really good too.

I switch this out routinely with a higher fiber but also higher carb lunch or dinner (in terms of keto.)

While I realize carbs introduced through dietary fiber are different I still don't like having them when the whole point of this diet is to reduce as many carbs as possible.

Some other good higher fiber veg that works in breakfast for me specifically is sauerkraut, cabbage in genera, steamed and mashed cauliflower/broccoli with some nice sautéed bacon and garlic.

That's just for fiber though.