Official Honda service manual online subscription: https://techinfo.honda.com/rjanisis/logon.aspx
1 day for $25, 30 days for $125, 365 days for $1250.
This is what the Honda dealership technicians will have. It will probably have the best explanations and diagrams.
I have read that this online system limits the number of downloads per time period now.
People in the past have bought a one day subscription and downloaded everything for their car in PDF form.
The manuals that Honda stopped producing are the books such as my 2003 Honda Pilot service manual
AllDataDIY that people have mentioned does not have any 2021 Honda manuals at this time. Official Honda service manual would be preferred over this anyways. Independent shops probably have the shop version of AllData (note this is separate from AllDataDIY) https://www.alldata.com/us/en/plp (see AllDataRepair)
Haynes and Chilton manuals don't have any 2021 models at the moment. These are third party companies and I personally would prefer a OEM (Honda) service manual.