there’s probably nothing specifically for tools to download observations, but there have been a few attempts – though none very exhaustive – to catalog things that people have made to work with iNat data:
- https://forum.inaturalist.org/t/external-code-tools-etc-for-working-with-inat-wiki/15906
- https://forum.inaturalist.org/t/3rd-party-inaturalist-tools/25971
the more specific you can be about what data you’re trying to get and what tools / skills you have, the better suggestions i might be able to provide.