alt + left mouse button anywhere in the window (maybe win button or something is default now).

using the titlebar for moving a window is extremely backwards and productivity killer.

that being said, I agree with you, and I think its an outright abomination to put the tabs in the titlebar, and its disgusting how crome and firefox by default removes the real titlebar

Alt+LMB drag is impossible to do properly, at least on Windows, because too many applications use that for their own inputs. There are some X11 applications that also use that (Blender?), so while it's cool when it works, it comes with pretty severe problems.

Alt-drag works perfectly well on windows. I use a third party app called alt-drag to enable it. Has worked fine for years.

It also allows you to use it with win-drag of course.

there might exist some programs that do it, but this might be why they changed default from alt to win key.

in either case, that appears to be the very extreme minority of cases you have to move a window