Match your use first: choose a “melt-friendly Swiss” for gratins/fondue, or a “slice/grate-friendly aged cheese” for boards and sandwiches.
Swap comte using the 1:1 ratio by weight, then taste after adding other salty ingredients (broth, seasoning, cured meats).
If the substitute tastes sharper than comte, add a small knob of butter or a spoon of cream to round it out during cooking.
If the substitute is too mild, increase flavor with a touch more garlic, mustard, or black pepper rather than adding more cheese.
For best texture: shred for even melting, and let melty cheeses warm 1–2 minutes before serving.