My understanding of the gut biome is that strains of bugs thrive if fed, and die off if they are not fed.
So by switching to carnivore, the strains that will flourish will be the ones that thrive on the foods I carnivorous foods.
Sure, the others will die off, but do I need the ones that eat fibre and veg and carbs and sugars, and so on? If I'm not eating those, then I don't need the bugs to break them down, and they were redundant anyway and will have simply starved.
The only strains that I want and need are the ones that benefit me - but that in itself is a vast subject, and one I am not able to discuss it with any knowledge.
This wiki article just skims the surface
https://en.wikipedia.org/wiki/Gut_flora
They (the bugs) serve a lot of different purposes, and I simply don't have any evidence that eating carnivore long term will be good or bad except for a few key pointers:
- the PaleoMedicina people report that strict keto carnivore improves/reduces gut permeability (and therefore autoimmune conditions), although it may take up to 3 years to do so.
- my own guts are happier on carnivore than on any other way of eating I have tried. I feel no need to inflict the details on you

but trust me, things are MUCH more comfortable.
- I take the view that a healthyish gut can cope with fibre, and fibre was part of a prehistoric man's evolutionary diet, but that would have been in the form of seasonal foods (which are self limiting), and often labour intensive to gather (which also limits their intake).
- an unhealthy gut often struggles with fibre, and does better without. Certainly this is the case for me.
I have now been carnivore for over 18 months (due to the repercussions of a particularly severe case of gut rot).
Attempts to reintroduce veg and fibre have been unpleasant. No, they have been VERY unpleasant.
I am happy continuing as I am, with (presumably) a less varied gut biome, because I feel well on it.