A ‘real’ EMS doesn’t exist yet. At least not one that ticks all the boxes. There is EMHASS: An Energy Management for Home Assistant, but it is somewhat limited in functionality and technically challenging to setup. Then there are lots of companies selling an EMS as part of their product range, such as solaredge. But the EMS then only works with their batteries and their PV and a selection of external products.
There are upcoming standards to standardize communication between an EMS and an energy consumer / producer, mainly S2 by TNO and EEBUS. Whether one of them will survive, or they will somehow merge, is not sure. IMHO the EU needs to write up a directive to force companies to support such a protocol, because the market is way too fragmented at the moment.
For PV forecasting you can ofcourse use the solar.forecast integration. But I found it lacking in configurability, accuracy and it’s quite an unreliable cloud service (but it’s free, so can you really complain…?) Anyway, I started pvcast for these reasons. With pvcast you can build a model of your PV system and do local solar forecasting with any weather forecast as input.