Dear Rasto Janota,
Thanks for using Microsoft products and posting in the Community.
I understand that there is an issue with automatic archiving of your Gmail account when using Outlook. Thank you for your efforts and attempts. This situation is indeed troubling, and I am very willing to help you.
May I ask if the Gmail you have configured is using POP protocol or IMAP protocol? Can you provide a detailed screenshot of your question?
In Outlook on Mac, you can check if the settings under Settings--Reading--Swipe feature have set the option to swipe to the save folder.
In addition, we suggest that you check your rule settings to see if you have set any rules for mobile mail. If there is, you can disable or delete it to see the effect.
Please feel free to let me know how it goes. If there is any deviation in my understanding, please forgive me and provide me with more details. I am more than happy to continue to help you.
Best Regards,
Addie.C - MSFT | Microsoft Community Support Specialist