Hi,
I am currently migrating SP 2013 to 2019 and found some differences in the Report Viewer Web Part. The new one connects to the Report Server and uses the web service it seems, while the 2013 one, connected to the Report Manager.
I'm not sure why, but it seems that in SP 2013 the web part delegated credentials without no problems and in SP 2019 I'm having problems delegating credentials to the SSRS, if he is installed in other server.
I think I have some ideas on how to begin, but I would like to understand what are the differences in both web part versions so it makes sense to me.
Cheers