When MongoDB submitted the Server Side Public License to the OSI for approval, the OSI has publicly announced that they do not consider it an open-source license.
Has the FSF (or, if relevant, a prominent member) ever commented on the SSPL in a similar fashion? As of writing, Wikipedia states that it is not "FSF approved", but despite my best efforts at searching, I can't find any comment from the FSF on the SSPL, not even in their list of licenses.
I dig some digging, and found RMS confirming in Oct 2021 that "we", presumably meaning the FSF, had still not got around to considering the SSPL, saying that it wasn't a priority for them, and that he didn't expect they'd find it to be a free licence as and when they did get around to it.
That was about a year and a half ago, and a full three years after the release of the SSPL. Given how little discussion I've seen about the SSPL in the last 18 months, compared to the furore that surrounded its publication, I can't imagine that the FSF would have seen any good reason to bump it up the stack since then.
That said, I freely accept that absence of evidence is not evidence of absence, and will be fascinated to see if anyone can dig up fresher data.
As your question acknowledges, the SSPL does not appear on the FSF's license list. Given how comprehensive this list otherwise appears to be, it is my interpretation that the SSPL's absence indicates that the FSF has not formally evaluated it. If they had, they would have put it on the list. The list contains many licenses which the FSF describes as non-free or otherwise problematic; licenses are not excluded from the list simply because the FSF disapproves of them. It is rather implausible to me that they would exclude the SSPL from this list, yet simultaneously take an official position on the license in a different forum.
Having said that, it is not clear to me how often they update this list. A date in the footer indicates March 4, 2023, but it looks automatically generated, and it might simply indicate that e.g. someone refactored the HTML or CSS without changing the contents of the list. It is possible that the FSF has gotten out of the business of evaluating licenses altogether (or at least, evaluating licenses that everyone already knows to be non-free, anyway).
