Since when do you need a custom compiler??? Both GCC and clang can build Linux RISC-V binaries with no problem. You didn't bring up extensions, but that's what

Since when do you need a custom compiler??? Both GCC and clang can build Linux RISC-V binaries with no problem. You didn't bring up extensions, but that's what people usually mean when they complain about fragmentation. It's not an issue in practice, just target RV64GC and you'll be fine. That describes the extensions which you can expect any general purpose computer style RISC-V CPU to implement. I wish the booting story was better though, for both RISC-V and ARM. Manually editing device trees sucks. But that's more an issue due to the lack of UEFI on these SBC style platforms, not an inherent issue with ARM or RISC-V themselves (in fact, in the server world, ARM systems with UEFI is common).