Nextcloud offer Enterprise support
https://nextcloud.com/enterprise/but hey, it's not Microsoft.
RedHat has always sold Enterprise support.
But it's not Microsoft.
There are many little realty that tries to live offering support for opensource solution.
But they are not Microsoft.
In Italy, there is
GARR, "a non-profit association founded under the auspices of the Ministry of Education, University and Research.".
When COVID lockdown striked, GARR started to offer opensource solution for schools, but nearly noone used it, someone started with Google School, someother with Teams, or Zoom. Right now the government (the same "Ministry of Education" as above) is pushing a solution based on office365/Teams. Wich incidentally is illegal unger GDPR.
Because GARR is not Microsoft.