There's that recent case of a woman in Australia who has been accused of poisoning family members with mushrooms:
Three people died after they were allegedly served poisonous mushrooms in regional Australia in 2023.
www.bbc.co.uk
Like 'findingquiet' just said though- I suspect it's very prolonged and painful. I think with these sorts of things- slow deaths, you have to consider how long you think you could put up with pain, not knowing 100% you will actually die from it and, not be tempted to call for help. I suspect it also depends on your own health. Someone with poor health already is going to be more likely to be affected. Like always with DIY methods, it's all the unknowns that trouble me.
Plus, I'm crap at things like identifying plants. I'd probably spend hours working up the courage to eat the things and they'd end up being normal mushrooms knowing me.