Apparently, after November 14, 2022, MySOS will be replaced by
Visit Japan Web
This looks to be web based as opposed to app based and will reportedly generate QR codes not only for quarantine but also immigration and customs.
I look forward to hearing real world experience in the next month. I'm not the happiest with it being web based but, oh well
My trip isn't until February so I fully expect a new iteration or 2 before then