How to get views machine name in `block--views-block-html.twig` file?
Views machine name would be: /admin/structure/views/view/frontpage.

You can edit/change the view name on right corner: Edit view name / description.

You can override the template name using below.


[base template name]--[view machine name]--[view display id].html.twig
[base template name]--[view machine name]--[view display type].html.twig


So this would be:


views-view--frontpage--page.html.twig


or:


views-view--frontpage--block.html.twig


There is no theme information is displayed with D8 views as D7 views was having the those information.

Please refer the reference page.