This makes the indeterminate HTML attribute available for use.

.changeset/ten-poems-remember.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+This allows a User to set the indeterminate HTML Attribute by adding it to the list of HTMLAttributes.

packages/svelte/elements.d.ts

@@ -808,6 +808,7 @@ export interface HTMLInputAttributes extends HTMLAttributes<HTMLInputElement> {
 	formnovalidate?: boolean | undefined | null;
 	formtarget?: string | undefined | null;
 	height?: number | string | undefined | null;
+	indeterminate?: boolean | undefined | null;
 	list?: string | undefined | null;
 	max?: number | string | undefined | null;
 	maxlength?: number | undefined | null;