So a few things about Sonarr, it has a very limited number of indexers so you definitely need to set up Jackett in the same system. This is exactly what I did and Jacket is pretty much self managed but you need to add it to SystemD for auto startup. One its automated it has a very long list of indexers and the actual up to date web addresses for those indexers which is key! All you have to do after is set up Sonarr to contact Jacket for a specific API that then gets translated to an actual indexer, it sounds more complicated then it actually is.
The one complaint I do have is that Sonarr really likes being in charge and expects the downloaded files to be on its own system and if it doesn’t get its own way it complains. Which is different from SickRage because Sick did not care what happens to the file once it is flagged as found which is just what I want. Since freeNAS uses zpools to control my storage I would never need to resize or alter how much space I need for transmission (running in a jail), however if I give Sonarr access to the SMB share that has the files it will copy them into its local directory. Now yes I can mount that local directory to the zfs dataset of my choice but if Transmission puts it in the same place that I want it in, what would be the point. Realistically i just need to shut down that post processing feature but Sonarr really likes to complain about it not being on which is only slightly annoying because who wants to see a constant alert on their dashboard. If I do just leave it as is then you start building up a queue of Sonarr waiting for the files to be available.