You state in your question that you have not yet filed your ATAS application. The UK government page on student ATAS procedures is here. That page contains this text:
How long applications take
Student and researcher ATAS applications take at least 20 working days (4 > full weeks) to process. If you apply between April and September, it can take at least 30 working days to complete. [Emphasis added]
Towards the top, the same page says:
If you’re a new student and need an ATAS certificate, you will need to get this before applying for permission to enter the UK [i.e., a UK visa].
When you have received your offer from your university you should apply [for your ATAS certificate] 6 months before your course will start. [emphasis added]
An ATAS certificate is valid for 6 months from the date it is issued, to enable applicants time to apply for their visa.
You should apply for your ATAS certificate as early as possible from when you have received a conditional offer to study at a UK Higher Education Institution (HEI).
Make sure your ATAS certificate will not expire before you apply for your UK visa.
At this point, only 6 weeks remain between today (October 17) and the beginning of your course on December 1. And you cannot even apply for a UK visa until your ATAS application has been filed and granted.
UKVI says applicants should should apply for ATS certification 6 months before the course will start, and allow twenty working days (4 weeks) for the ATAS application to be processed. It is therefore far from certain that the ATAS application and the subsequent visa application will both be processed quickly enough to allow you to travel to the UK to begin the course on December 1, 2022.
While you may be successful, it is more likely that you have left this too late. I wouldn't buy tickets to the UK yet; if you do buy tickets, make sure the tickets are fully refundable in case either the ATAS application or the following UK visa application are delayed or denied.