Nope. From what I see they just some released preliminary documentation, other essential documentation is missing and there is no software support yet. But nevertheless these devices look very interesting.
I mean, every FPGA vendor announces the chip's capabilities well in advance of them getting to the customers, but once announced with a feature list, they're
almost certain to appear in due course.
Gowin's IP list is pretty impressive. Their software is very (very!) bare-bones - nothing like the complexity of the big two. In some ways that's appealing... In others, downright annoying.
What is sorely lacking is the sophistication of their IP - in my aborted attempt to port BrianHG's DDR ip to the Gowin chips, the difference between the Altera and the Gowin IP was stark. The documentation reflected that...
On the other hand, the chips are very very cheap for what they do, the IP is all freely available, and the software is fairly straightforward to get working with ModelSim - they provide the simulation models that modelsim can read, for the Gowin primitives.
So, you pays your money, and you makes your choice. The uplift from the 9K to the 20K board from SiSpeed is quite significant for $7 difference, and it's on a nice form-factor SO-DIMM with DDR already mounted. As a 'build-in' module, that's a pretty good deal under a lot of circumstances, IMHO.