Because Hardstyle often overlaps with Hardcore in osu!, you should look for "Theme" packs or community collections.
If you want to build your own pack, these recent uploads are currently popular in the community: osu hardstyle beatmap pack
200 MB | Difficulty: 5* to 8* In 2023, a niche tournament called "Scuffed Hardstyle Cup" released their mappool to the public. This is a small but brutal pack. Because Hardstyle often overlaps with Hardcore in osu
You can find several "Various Artists" compilations or specific remixes tailored for hardstyle fans: osu hardstyle beatmap pack
Balanced tracks (150 BPM) with melodic breaks and heavy drops.