I confirm middle click failing to open in new tab on Linux Ubuntu 22.04, even after enabling Enable tabs (it opens in current tab, which is worse than not doing anything at all because you may lose form content). Right-click > Open in new tab works though.
I often write some review post, check info on the game in a different tab, and finish writing the post. But since middle click failed it replaced the current tab, and when I went back my post draft was lost… This only happens in the itch app which seems unable to save form content. In a browser like Chrome, pressing Back restores the previous page and form content. So it’s even more important in the itch app.
For now, I’ll make sure to review things as much as possible in the browser, and use right-click > Open in a new tab when I really need multi-tab in itch app.