Project for 3 years destroyed by plastic scm "upgrade"

I started the project in 2019 with unity version 2019.1.6f1. Unity collab worked perfectly for me. I didn't need any "upgrades" or "more robust system." However, recently, the unity collab system was deprecated and I was forced to switch to plastic scm to have my project saved in the cloud if I didn't want to zip my multiple GB project and upload it to google drive every time I modify a script.

Since 2019.1.6f1 was not supported by plastic scm, I had to update my editor. I used 2020.3.30f1 as it's a long-term support and "stable" version. The first time I opened the project, it worked fine and I was able to upload the project to plastic scm. However, starting from the second time trying to open the project, without having modified any part of the project, the editor gets permanently stuck on this screen every single time I try (restart pc, delete library folder to reimport, nothing works):



After no success in attempting to resolve this issue, I tried using the newest version of unity recommended in the unity hub (2021.2.17f1). Upon loading the project, the editor now tells me that some of the API used in my scripts have been deprecated (backwards compatibility just isn't a thing in unity???) and in order to open my project, I would have to let the editor modify these scripts to fit the new API. After the editor opens, it prompts me to log in. Every time I click "sign in with Unity ID," I'm treated to this glorious screen:



And every time I try to manually type in my email/password, this is what comes up:



And when I decided to give up on plastic scm and just zip my multiple GB project to google drive every time and tried to open the project on 2019.1.6f1 (worked perfectly fine with unity collab!), it tells me that the scripts have unrecognized content (since they were forcefully modified by 2021.2.17f1), the project can no longer compile.

3 years, hundreds of hours of work, flushed down the toilet by this new, improved, and robust version control system.

Now, since I was able to upload a functional version of the project to plastic scm when I first opened 2020.3.30f1, I'm asking to see if there is a way to pull that upload from the cloud. 2020.3.30f1 will now get permanently suck on the screen I showed earlier and won't get to the plastic scm screen at all, and 2021.2.17f1 won't sign me in at all. So is there a way I can pull the entirety of my project from plastic scm without having to go through unity editor, or is there a version of unity editor that actually functions as a game engine and also supports plastic scm at the same time?

I'd really appreciate ideas on how I can potentially work around this issue.

 

Hi, thank you for your assistance. I was able to recover the entire project from the external client. I should mention that "sign in with Unity ID" continues to show the same error page even when prompted through the plastic scm client, but the email/password login works in the client. I apologize as I wasn't able to recreate the issue where the editor is permanently frozen, but if the issue comes up again, I'll make sure to provide the log files.

The recovered files now work normally in 2020.3.30f1, but it seems like unity engine now no longer shows the plastic scm window for this project and attempts to use the now deprecated collab system. That's not an issue as I can use the client to upload my changes.