I have 7 out of 8. I just need Protozoa. (I see others suggest looking for slime mold.)
I got virus only because some came with the bean seeds I bought. Unfortunately, Bean Common Mosaic Virus is not in the iNaturalist list yet.
(I noticed some people submitted their positive COVID-19 test as a virus observation, but I hope none of you need to go this route for your virus observation. Just look for SARS-CoV-2 or Severe acute respiratory syndrome-related coronavirus ssp. 2)
From a visit to Yellowstone: Bacteria and Archaea. (But I don’t think these will ever reach Research Grade.)
From the seashore: kelp.