@jimw Regarding the baudrate: My point is that the shipped hardware seems to not have the weird (89856) baud rate but just half of 115200 (57600). Maybe this is due some differences of CPU frequency between earlier versions (used in testing/to write the documentation) and the final product? I noticed that the factor of 1.196GHz/1GHz is not too far off of the 33MHz/26MHz that you stated above (but clearly not the exact reason).
Regarding peripheral support: The “list” you mention are the devices that are explicitly mentioned in the SW Reference Guide, right? This is basically one single NVMe SSD and one single SD card. :)
Maybe we could organize a user-curated list of tested devices like many open-source projects do. For example, flashrom generates a list of the implemented hardware with test status. The easiest way to do something similar would be a sticky thread in this forum where people post the hardware they have tested. This is very unorganized but would not require any resources. A git(hub) repo where people can add devices via pull requests would be another way but that’s quite bureaucratic. A user-editable wiki (hosted by SiFive) would be much better from my PoV - not only for this but also other things like guides (e.g., to enable booting from SPI).
After all, it is not as bleak as one might think from the statements above. I could (almost) successfully boot from a SATA SSD attached to a PCIe controller card in the PCIe slot with U-Boot coming from SPI flash, i.e., w/o SD card. :) (It hangs at relocating the kernel ATM… that should be fixable). It needs some U-Boot customization but apart from the known SPI patches it is just configuration changes to enable the controller and SATA (yet).