obs_lsst provides camera descriptions for data that looks like LSST data, including that originating from test stands, ImSim, and PhoSim. As such, this package effectively renders obs_lsstSim obsolete. However, the future of obs_lsstSim is discussed on RFC-533: this RFC refers only to adding obs_lsst, and takes no position on deprecating or removing obs_lsstSim.
obs_lsst has been largely developed outside the regular DM development workflow. However, the code has recently been reviewed by Colin Slater, Tim Jenness and Wil O'Mullane. This review has resulted in a number of Jira tickets being filed requesting improvements to the obs_lsst codebase: here is a complete list. I propose that
DM-17291 and DM-17299 are prerequisites for adopting obs_lsst (ie, they will block the implementation ticket for this RFC); the others will be added to the DM backlog and scheduled as regular work.