Downgrading from Microsoft 365 Personal to Classic on Apple-purchased account

First, a warning: this is not a solution for what you want to do but has some information that may help you rule out many options and see a number of other users failed attempts.

I noted your post because I am subscribed to Microsoft 365 Personal directly through Microsoft, my subscription was about to expire (I had auto-renewal turned off). I turned on auto-renewal so that it would renew and then noticed that the price had gone up from $69.95 to $99.95. I then did a little research and as a result I went to my Microsoft account page and clicked the button to cancel the subscription and was immediately offered the option to switch to the non-AI "Classic" Personal version at the $69.95 price. I may have been lucky because I have seen many other users subscribed directly through Microsoft that weren't able to. I may have succeeded because I had auto-renewal off and because my subscription was about to expire.

When I saw your question I did some more research and found reports of the following (none of which I can personally verify):

1. It seems that in addition to subscriptions through Apple, it is not possible to switch to Classic if the subscription is through the Google Store or if the subscription was purchased through Amazon.
2. It seems that it is not possible to cancel the subscription (no matter how it was purchased) and then subscribe to Classic directly through Microsoft. That is, it seems the only route that has worked is to start the cancellation process on a subscription that is directly from Microsoft and then make the switch to Classic before completing the cancellation. Even then, many are reporting inability to switch or problems in accomplishing the switch.

Some other discussions in Apple and Microsoft forums that may be of interest but that don't solve your problem:

downgrade to microsoft 365 classic - Apple Community

and

https://answers.microsoft.com/en-us/msoffice/forum/all/downgrade-to-classic-m365-personal-through-apple/f0055eb2-0964-4673-9fef-fc3fbdaea548

and

https://answers.microsoft.com/en-us/msoffice/forum/all/the-option-to-switch-to-microsoft-365-family/d7a38829-7d1c-4328-813c-8fb90bde9294?page=1