What guidance is available for implementing hydrogen flame detection using IR cameras? Specifically, what are the recommendations for filters? What about camera characteristics, maximum distance, and so forth?

One pertinent reference is a Sandia National Laboratories paper by Schefer et al: Spatial and radiative properties of an open-flame hydrogen plume, Intl J. Hydrogen Energy, 31 (2006): 1332-1340. Information on this and other similar papers are available at https://h2tools.org/bibliography. Further information can probably be obtained from the author of this paper and other papers reporting hydrogen flame spectral distributions. Of course, hydrogen flame sensor manufacturers also have such data and should be consulted.  Specifications on these sensors should provide useful data.