I'm looking for hairstyles converted from The Sims 4, but also set as default replacements. I've found a couple of 4t2 blogs, but they have very few hairs (and none of them are replacements).

Any help would be appreciated.

Have you tried the default database? You could pick up some creators there.
https://sims2defaults.dreamwidth.org/
If you scroll down you can see recent updates, and you can also click on the hair categories.

A lot of conversions are on Tumblr these days. Creators like DeeDee and RentedSpace tend to have conversions, and various creators tend to make these into defaults.

This one seems to have several:
https://daruebersims.tumblr.com/tagged/default

As for conversions:
https://sims4t2conversions.tumblr.com/tagged/dl-hair
https://rented-space.tumblr.com/tagged/4t2-conversion
https://deedee-sims.tumblr.com/ (not sure if she has mesh conversions, but there's plenty of MM recolors)
https://mdpthatsme.tumblr.com/ (little bit unsure about hairs, I think I've seen a few)
Google "sims 4t2 hair" and you can probably also find a few useful links.

Thanks, I have tried the default database, but most of the hair on there isn't Sims 4-styled/"clay" styled. I'll check out the blogs.

The problem is that there isn't much destinction between 4t2 CC conversions and 4t2 from ingame, so you'll often have to look around. Creators who do a lot of ingame conversions from TS4 like rented-Space, MDP or DeeDee can be a good starting point, and Tumblr is a rabbit hole once you start clicking links.

If you're after low-poly hairs and not just "clay", TS3 ingame conversions aren't too bad either. They're often roughly in the area of TS2 hairs, and those three tend to have several of those hairs. Trapping is another creator you might want to check out for 3t2 (has her own page, but also a lot on GoS and various other sites).

If you search for EP-spesific names (like "EP04") or the names of the TS4 (or TS3) hairs you want to find, you could get better results.

Other places to look for conversions are GoS and updates at Simscave:
https://gardenofshadows.org.uk/gard....php?board=57.0 (particularly themes and events - it is a bit messy, but you can find a lot of creators this way)
http://simscave.mustbedestroyed.org...3cd&board=172.0 (don't get lost...)

Alright, thanks.