IMDb now has an “adult animation” tag that is worth looking into.

I’d suggest:

• Fritz the Cat (1972)
• Fantastic Planet (1973)
• Heavy Traffic (1973)
• Wizards (1977)
• Fire and Ice (1983)
• Rock & Rule (1983)
• Gandahar (1987)
• The Haunted World of El Superbeasto (2009)
• The Spine of Night (2021)

Series:

• Spicy City (1977)
• Æon Flux (1991)
• The Maxx (1995)
• Love, Death & Robots (2019) - an anthology series so a collection of shorts
• Primarily (2019)
• Too many on Adult Swim to make a complete list of but Metalpocalypse and Mr Pickles stand out in this context