I really don't see how SN could be made look like an accident, it has very clear effects on your body, like your lips turning blue among other things. Not to mention that this is not something that you ingest in quantities larger than a couple of grains in meats, and people are not expected to have it laying around unless you are a fisher or a butcher.
Or, well, There can be a way, but I want to be VERY clear about this, I don't recommend, nor encourage and much less want you to do this.
You could probably pass it as a case of death by coronavirus IF you live in an area deeply affected by it, manage to hide all evidence, get tested and your family knows about your results and get a bit of luck. many hospitals are getting overrun so they don't really have the time to investigate each death and rule it as suicide, specially when there was already a confirmed diagnosis and some form of testimony about it.
Still, this is highly unreliable and you'll probably have to accept the fact that they'll know it was a suicide if you decide to use SN.