Same issue more or less, I am sending tabs from an android phone and tried to send to both Windows and Linux and always have the issue. Worse they open in a private tab so I can't just drag and drop them onto my other one. It's happening since the last update. I'm using the last version available on all of them.

Thanks for the added details. This corresponds to my issue, as well: Android mobile to Windows 10 Desktop. Latest versions of everything. Sent tabs opening in private window.

Same, it's opening in a private window. It's a real nuisance.

Yeah, I’ve noticed that behavior too it’s pretty annoying when it suddenly changes. It might be related to a recent update or a setting reset. You could try checking your tab settings or disabling/re-enabling sync to see if it fixes it. If not, a quick reinstall or updating Firefox to the latest version might help.