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I’m not sure it’s going to be worth trying to compile all those account names, going through 18 pages of threads, and then paging within each of these threads, to determine the names of those accounts created within a given month. It seems like a pretty time consuming manual task.
In any case, If I were to be inclined to do so, I’d probably try to use ninjastic as an accelerator. It doesn't have all you’d need, but it should save a lot of time. For example, the following query lists 455 profile names that have posted in B&H this month to date. From there on, you’d need to enter each profile and check its "Date Registered" value of the user’s profile (*):
https://ninjastic.space/search?after_date=2022-05-01T11%3A07%3A17&before_date=2022-05-31T11%3A07%3A17&board=39 (go to user's tab and press "Generate")
(*) Ideally, you’d be able to cross the above 455 names with another source to automate deriving the "Date Registered" dates. I don’t recall their being an already existing and updated file generated by anyone with this information, so with time, you could eventually adventure into scraping the said profiles …