Note that there are many RISC-V variants. There is a 16 bit version, which may make a nice toy if you want to play with an FPGA. The usual hardware in production seems to be the 32 bit flavor. There is a 64 bit design, as well as a design with a 128 bit address space. This is university research after all.
The RISC-V is the darling of some components of the open source community. I find this a bit perplexing -- the typical "hacker" is not going to start producing parts in silicon, and while you could certainly put the design into an FPGA, I don't really see advantages to doing so. ARM processors are available and cheap. I don't mind if ARM makes some money licensing them.
The main appeal is for reasons of "PMS" (perceived moral superiority). There is no particular technical merit when compared to an ARM or Xtensa processor.
All this being said, there is absolutely nothing wrong with the RISC-V, at least not that I have discovered in my dealings with it thus far.
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