What is the difference between Buddhism, Hinduism and Solipsism? Do all these religion say that other people have no mind's? If all these religions are like solipsism, then are all Chinese and Hindus solipsists?
In Hindu thought all minds are manifestations of a fundamental unified awareness, Brahman. In dualistic traditions the manifestations are separate to Brahman. In non-dual traditions they are not separate. I would say this is different to solipsism, because Brahman gains new real knowledge from the interaction of these manifestations. There is both individuation, and reintegration through religious practice towards unity. Centering our lives on the part of us which is more universal, is understanding our atman, the part of which relates to Brahman. Strands of Hinduism have been interpreted or criticised as solipsist since at least 1000BCE. In Hindu thought all minds have a transcendental unity.
In Buddhist thought there is no transcendental unity. Oneness is Buddhist thought should be understood with emptiness of sunyata, as relating to 'one taste', that non-duality is fundamental, all minds are made of the same kinds of processes. Indra's Net originates as a metaphor to illustrate emptiness or dependent origination, in Hindu philosophy. But it has been given special prominence in Buddhist thought, where deconstructing the intuition of the conventional permanent unchanging self is a key pillar of the practice. Buddhist thought explicitly deals with accusations of solipsism, through considering dependent arising, and identifying the Buddhist path as the middle way between nihilism and eternalism (no meaningful self, pictured as, permanent or unchanging essence). In Buddhist thought all minds are fundamentally dependent on causes and conditions, and are empty of any permanent, inherent or unchanging nature, or essence.
Solipsism cannot meaningfully be asserted as a philosophy, because why would any serious holder of the view care what anyone else thinks? But it has served as a philosophical tool in Western thought since at least the pre-Socratic Georgias, right up to very modern arguments about 'philosophical zombies' popularised by Chalmers & Dennett. While metaphysical or epistemological solipsism are difficult to hold consistently, methodological solipsism as proposed in Descartes 'cogito', is widely used, and is essential to substance dualism. I would say the physical reality of information, and the dependence of sophisticated conceptual thinking on the community practice of language, make both solipsism and substance dualism untenable. But you did not ask for a critique of solipsism, so I will end there.
I've read a few comparative studies, and as far as I know no-one has ever claimed this. but, I can I think see what motivates this question: if "I" don't exist, then nobody does.
I think the mistake there is to wrongly think that, because there is no substantial and unchanging "self", other people are complete phantasms. Void in the sense of not belonging in the world at all. That is nihilism.
The alternative unravelling of the question, is that solipsism says "I" exist, and usually this means substantially.
So much for early Buddhists as solipsists.
Tientai / Tendai Buddhism famously talks about one thought containing "the three thousand dharma realms". I think each world is meant to mutually include every other, so claiming that your world exists and no other, is a mistake. I think this means it more like the ending of the flower garland sutra, in which every thought (your thought of enlightenment, my suffering) already contains every other, except that this does not for a moment eliminate your own inclusion in every world.
nb I am no expert, just saying that the middle way denies the separate existence of yourself and others.
Russell famously found solipsism just confusing, as if anyone could try and justify such a claim to anyone.