I have read that Chad and Libya still practice slavery. Sex slavery, I have read, is still rampant throughout the Islamic nations.
Modern slavery (or, neo-slavery)
The two countries you cite (Libya and Chad) are failed states. There are others. Tribes do as they want. We civilized humans aren’t far removed from savages.
Other contemporary forms of slavery: North Korea and Cuba and possibly other countries rent out their people to other countries for hard currency or commodities in demand.
China uses prisoners as a source of slave labor, often meting out harsh sentences for minor crimes or no crimes at all. (In a similar fashion, it executes criminals for organs.)
Saudi Arabia allows guest workers some or even many of whom are treated like slaves.
Criminal gangs kidnap or entice girls into lives as prostitute using a combination of coercive force and drugs.