Don't underestimate the rage from citizens who receive important documents and sheets in formats they can't open. Or you can open them but with a warning that some functionality might be lost. (reads like: you might go to prison)
I can't think of any official documents I'd be getting in Office file formats. Forms are mostly web ones or in some cases PDF, read-only documents are PDF. Maybe you can submit some documents or attachments in the Word format as a citizen but I wouldn't be surprised if PDF is already required anyway, or an image format for scans.
I'd be more worried about document interoperability between government agencies and other organizations such as companies that do work for the government. The government could of course mandate contractors to use an open source office suite which would extend the need for training to those companies.
Also, I've seen some orgs make heavy use of Office formats in terms of e.g. surprisingly elaborate formatting, document history and comments, and although I haven't tried to use those in LibreOffice, I wouldn't be sure it supports all of those in the same extent some people have learned to use them in Office.
My gov is moving 100% of documents, forms, official stuff to web based without browser plugins. Of course unfortunately if you want to download/print (...) it will be pdf, but outside that, all filling in, editing, reading etc of all citizen facing materials must be possible with a modern web browser. If PDF is only the export for the final doc, I am ok with it; I can fill ut with whatever browser on whatever device. This should be the mandatory basics imho.
Things can be done in such ways that there is nothing visibly incompatible (ie scripting behind some forms), you can always just print and fill the document if needed, and anyway most documents are static pdfs with optional plus for filling some fields in computer.
For us it isn't a very big deal. We will dig out the data points with our bare hands if we have to. (in ways that would make a data analyst scream) For normal users the experience is more like ransomware.
I really hope that happens but I see those announcement as negotiating tactics. Switching will cost a lot (in training, unavoidable delays and mistakes etc.) and both parties will have incentives to go back to good old days.
I hope I am wrong on this. I hate that public infrastructure and bureaucracy runs on Microsoft.
