Do not wrap custom block in an additional DIV but instead use only the JSX I provide

by

Update: WordPress 5.6 will be released soon and this will include a block API version 2 which allows all these modifications noted in OP.
https://make.wordpress.org/core/2020/11/18/block-api-version-2/

I found a filter that allows me to modify the wrapper. Still, I can’t change the HTML tag, but it’s better than nothing.

const { createHigherOrderComponent } = wp.compose;

const withClientIdClassName = createHigherOrderComponent( ( BlockListBlock ) => {
    return ( props ) => {
        const newClassName = "block-" + props.clientId + ' sample-block';
        return <BlockListBlock { ...props } className={ newClassName } />;
    };
}, 'withClientIdClassName' );

wp.hooks.addFilter( 'editor.BlockListBlock', 'awps/modify-blocks-wrapper', withClientIdClassName );

And the methods:

edit: () => {
    return (
        <mark>Sample</mark>
    );
},
save: () => {
    return (
        <span className="sample-block">
            <mark>Sample</mark>
        </span>
    );
},