Ubuntu is the worst of the Debian based Linux distributions. Give MX Linux a try. It's rarely evangelized, unlike other Linux distributions, but it has a surprisingly high user base, and for good reason. Everything it has added to Debian enhances it, and it doesn't try to promote any services, like Ubuntu does with Canonical's services.

Regardless of the Linux distribution, it's still way to early to get good support for RISC-V. Current products are good enough for general development, but RVA23 was ratified less than a year ago, and I don't know of any designs started after the ratification that have hit the market yet. Once that's the case, it should be easier to get universal support, but until then, every RISC-V SBC is a one-off development board.