HaikuOS, and the BeOS it is essentially a continuation of, isn't linux-compatible and doesn't have that as a goal. It has its own kernel and OS stack.
Its not really any more usable as a daily driver on RISC-V than it was on any other architectures like x86, but RISC-V support is a milestone because its likely the applications where a very lightweight OS like HaikuOS would be most useful are things that would fit more into the "embedded" bucket than the "desktop computer" bucket - like others in the comments have mentioned, think media kiosks, display systems, hardware appliances, etc. For some perspective, BeOS was purchased by Palm (the handheld computer company) before that whole corner of the industry started dissolving in the smartphone era, so thats the kind of device it was being used on commercially.
(Also, RISC-V isn't ARM - your mainstream ARM laptop is probably going to happen especially now that Apple has shown they can sell well, but RISC-V is still ramping up towards that point of popularity.)
Its not really any more usable as a daily driver on RISC-V than it was on any other architectures like x86, but RISC-V support is a milestone because its likely the applications where a very lightweight OS like HaikuOS would be most useful are things that would fit more into the "embedded" bucket than the "desktop computer" bucket - like others in the comments have mentioned, think media kiosks, display systems, hardware appliances, etc. For some perspective, BeOS was purchased by Palm (the handheld computer company) before that whole corner of the industry started dissolving in the smartphone era, so thats the kind of device it was being used on commercially.
(Also, RISC-V isn't ARM - your mainstream ARM laptop is probably going to happen especially now that Apple has shown they can sell well, but RISC-V is still ramping up towards that point of popularity.)