Intuit have announced that they are discontinuing QBDT at the end of January 2023 (although I gather from forum posts that this is being put back to June 2023. I still don't know if my copy of QBDT will stop working before then.)
You state that you are working on a new service to allow QBDT to QBO migration yet you are still going to discontinue QBDT before it is ready. I can't help but feel that this is the wrong way round. Do you have a current date of release for the new conversion method? I notice that the post you link to: Why can’t I move my data from QuickBooks Desktop to QuickBooks Online? was last updated on 27 July 2022. Is there any further update on this?
Attached is a screen grab from the dashboard of my QBO account. there is no mention here that I will not be able to transfer my data. Why is this dialogue being presented on the UK QBO site?
I am aware of the movemybooks method (which you don't mention) but will have to spend about £450 to ensure that the HMRC mandated 6 years of data are transferred.
To be honest I feel as though I'm stuck in some Kafkaesque hell where my desktop programme (which has worked fine since the days of Quicken) is being removed with no means of getting my data to the online offering that I am now forced to subscribed to.
