Woah, that totally works! I would've never figured that out by myself. Thanks! 🙏ok I think I figured this out. You have to turn the phone sideways and long press on a tab in the tab bar. Then choose "arrange by title". This will flip around the tabs so you will reorder them but opening new tabs in the background should drop in the stack like you expect. I think what is happening is the new "arrange by website" option is active and the tabs are auto sorting.
Edit: tabs are definitely opening normally for me now.