There is chicken rendang (RENDANG AYAM/CHICKEN RENDANG), beef rendang, and of course, mutton rendang, or rendang kambing. Is the recipe very different? Not really. You can change some ingredients for a twist, but the core ingredients are a must.
Mutton is generally tougher than lamb. Cooking it until tender can take time. If overcooked, it will shrink and lose its texture. A useful tip for mutton rendang and other mutton dishes is to pressure cook the mutton with ginger paste and garlic paste. This makes cooking easier while keeping the flavor.