Who believes in the Flat Earth theory?
I will admit to having a foot in the "alternative' philosophies, mainly with an open mind towards esoteric systems of thought. I used to read David Icke at one stage, but did think that he was 'over the top' in his conspiracy theories, especially his idea that the Royal Family were shapeshifting reptiles. I think that conspiracy theories can be dangerous if they are taken literally, but are quite useful as unusual ways of looking and thinking.
Apart from David Icke, I have read Blavatsky, Rudolf Steiner and Benjamin Creme and many other alternative thinkers.
I read them less nowadays, especially since reading philosophy, in conjunction with reading and writing on this site. However, what is interesting is your choice of the words 'flat earth', because 'flatland' was the way Ken Wilber, a transpersonal philosopher, described many mainstream traditions of thought.
Personally, I like to read as widely as possible, and try to juggle various ways of thinking, ranging from the extremes of materialistic perspectives of determinism to the 'spiritual' alternatives of the esoteric thinkers. I believe that the 'truth' may be somewhere in between, but it is not clear and rigid because there is the whole symbolic dimension of reality. I believe that this may be why people are often drawn to the alternative philosophers.