themes-wordpress/quadrat/sass/blocks/_buttons.scss

@mixin quadrat_button_hover_styles {
	&:hover,
	&:focus,
	&.has-focus {
		border-style: var(--wp--custom--button--border--style);
		border-color: currentColor;
		border-width: var(--wp--custom--button--border--width);
		padding-top: var(--wp--custom--button--spacing--padding--top);
		padding-bottom: var(--wp--custom--button--spacing--padding--bottom);
		padding-left: var(--wp--custom--button--spacing--padding--left);
		padding-right: var(--wp--custom--button--spacing--padding--right);
	}
}
.wp-block-button {
 	&.wp-block-button__link,
 	.wp-block-button__link {
		&:not(.has-background):not(.has-text-color) {
			@include quadrat_button_hover_styles;
		}
	}
}
.wp-block-file .wp-block-file__button {
	@include quadrat_button_hover_styles;
}	

.wp-block-search {
	&.wp-block-search__button-inside .wp-block-search__inside-wrapper .wp-block-search__button,
	.wp-block-search__button {
		@include quadrat_button_hover_styles;
	}
}

.wp-block-post-comments {
	input[type="submit"], .reply a {
		@include quadrat_button_hover_styles;
	}
}

//NOTE: Double-classed to raise specificity above parent theme's outline hover styles
//as an alternative to !important.  Only needed for the editor.
.wp-block-button.wp-block-button.is-style-outline {
 	&.wp-block-button__link,
 	.wp-block-button__link {
		&:not(.has-background):not(.has-text-color) {
			&:hover,
			&:focus,
			&.has-focus {
				color: var(--wp--custom--button--color--background);
				background-color: var(--wp--custom--button--color--text);
			}
		}
	}
}