Theme preview issue

Likewise, what I do is go to https://wp-themes.com/ and then enter the theme name on the end to view the theme.
E.g,
https://wp-themes.com/blackbird

@john brown

That drives me crazy in Firefox sometimes too. You can also just “middle click” (with the scroll wheel on your mouse, if you use one) on the preview link, or “right click” > open in a new tab/window. Much better preview that way.