Obviously most scientists are not going to be interested in null results from adjacent subfields, but when it comes to specific questions of interest it is absolutely useful to know what has been tried before and how it was done/what was observed. I know a lab that had documentation not only on their own historical null results but also various anecdotes from colleagues' labs about specific papers that were difficult to replicate, reagents that were often problematic, etc.

That is a non-ideal way for the scientific community at large to maintain such info. Trying to go through traditional peer review process is probably also non-ideal for this type of work though, for reasons you cited. We need to be willing to look at publication as something more broadly defined in order to incentivize the creation of and contribution to that sort of knowledge base. It shouldn't be implemented as a normal journal just meant for null results - there's really no need for this sort of thing to be peer reviewed specifically at the prepub stage. But it should still count as a meaningful type of scientific contribution.