Thank you for your question.
TVM unity is currently being developed as part of the unity branch https://github.com/apache/tvm/tree/unity and is this case being frequently updated with robust community support. see more background here Establish TVM Unity Branch
For emerging needs that involves dynamic shape or stable diffusion, likely it is already the best(or only) robust path. So from maturity pov it is likely already matured(and more mature than relay since relay was not designed for first-class dynamic shape) for first-class dynamic shape use-cases. So if you care about emerging needs(e.g. LLM or SD) and dynamic shape is to your use-cases, have a go with it.
The support of frontend usually comes in a community driven way, right now it comes with ONNX and FX frontend. The overall cost of ramp up time of a frontend is reasonable and we are open for community to bring in more frontends, we also welcome contributions
Good point on the documentation, you can find the ML compilation course https://mlc.ai/ that teaches basic concepts, along with tutorials, some are posted in unity - Apache TVM Discuss