Sorry about that. Running into these problems every time there’s a new Ubuntu version is extremely annoying indeed. We are very close to fixing these issues once and for all (see https://github.com/brave/brave-core/pull/3750) by switching to a fixed “distro name”.
In the meantime, follow these instructions instead: https://github.com/brave/brave-browser/issues/6522#issuecomment-545672208