I keep a special laptop for all financial stuff. It is not that expensive and the inconvenience is limited. And on it I have CubesOS, but I guess OpenBSD would also be a good choice.
I assume you meant QubesOS not CubesOS which I don't know of. You can totally run QubesOS as a host, it helps for hardware compat and fs perf/stability, and run OpenBSD alongside Fedora or Debian VMs as guests.
