If you are an intermediate C++ developer or better, then my imageboard archiver/downloader might be of interest to you. You have to be able to manage installing prerequisite dependencies and have at least a C++17 compiler, but if you can this is probably already the single most efficient IB-oriented scraper out there, even though it's still just alpha code.

https://files.catbox.moe/yzrvle.7z
1b107d1eeead145d44c3f23d23e937feb14b4d41e23d13660f78d230be20a26a BUMP-0.2d.tar.xz