The recent SIESTA school produced a few valuable leftovers (apart from funny experience of hosting events on Discord). Those appear, most importantly, in a form of updated SIESTA Tutorials & Documentation , but not only.
There was also a set of video lectures prerecorded and released before the start of the school (as is trendy these days). The YouTube playlist is available here:
 Work in progress, where "progress" stands for organizers' tremendous efforts to deliver the general part of materials in time for the event, as well as to keep the project up-to-date afterwards.