is there a way to downgrade project version?

Short answer no. You can try to remove Unity and install older version for the download archive. Then start the project, if you are lucky it will reimport and work. Most likely, it will screw up the scene file.

I went through the same issue, you may have to remove the libraries related to analytics and other Unity services as those have been greatly changed lately. It worked for me to some extend. In the end, I had to resort to version control.

This is why you should always version control your project in GitHub/Lab or else. Then this kind of issue would not matter greatly.

Open the Unity Hub, find your project, click on the current version of Unity that is listed next to it, select an older version from the drop-down menu.