ICE40UP5K is large enough to synthesize a simple RISC-V CPU with some basic peripherals. It's not huge or fast, but it's capable enough.

Note, if you need a barebones CPU but want to save on gates, you can go with a serial (1-bit) CPU, e.g. SERV which only takes up 198 LUTs on ice40,[1] leaving plenty of space to do other things.

[1] https://github.com/olofk/serv

You mean it's large enough to synthesize several application specific RISC-V cores and let them form an embedded distributed system.