The North Dakota Libertarian Party recently decided to run Roland Riemers for U.S. Senate this year. He needs 1,000 signatures by early September, and expects to obtain them. This means that every state has minor party or independent candidates for statewide office this year (except in the two states, Kentucky and North Carolina, that don’t hold any statewide elections this year).
There is a good chance that almost all of these 48 states will have such minor party or independent candidates for statewide office on the ballot. The only state in which there is no chance that such a candidate will be on the statewide ballot is Alabama. In Illinois, the Greens will be on if they survive the challenge (it seems likely they will). There is also uncertainly about Pennsylvania and New Mexico; court actions will be important in those two states.