This one is a bit more colourfull https://www.evolution.unibas.ch/walser/bacteria_community_analysis/2015-02-10_MBM_tutorial_combined.pdf
On the forum on bias etc
Biases in iNat data - General - iNaturalist Community Forum
How to distinguish increased observations of a species from overall increased observations - General - iNaturalist Community Forum
Occupancy models in R Part 2: model comparisons (jamesepaterson.github.io)
You might be interested in rarefaction analyses that can help in partially taking into account varying observer effort across states. See the iNEXT package and this paper https://doi.org/10.1111/2041-210X.12613 .
https://forum.inaturalist.org/t/some-choropleth-maps-using-inat-data/21776/2?u=ahospers