Lezhin Comics sometimes has free manhwa available. It has a diverse selection, but you might need to keep an eye out for promotions and limited-time offers.
Mangatoon is worth trying. It has a decent collection and provides a smooth reading experience. Some of its features like bookmarks and recommendations are quite handy.
Tachiyomi could be what you're looking for. It's customizable and has a lot of sources for free manga. However, it might require a bit of setup to get it working just right.
Well, Webtoon is quite popular. It offers various genres of manga and often updates with new content. Also, it has some unique features like community interaction.
I'd suggest looking into apps like MangaToon or Manta. They sometimes offer free access to manhwa. Just make sure to check their terms and conditions for any restrictions.
You might want to check out Manga Rock. It has a decent collection of manhwa, and there's a chance you'll find some free ones. Just be aware that the legality of certain sources on such apps can be questionable.