This is not exactly the same as the editors of a journal changing the publisher of a journal, but let me put in a plug for "flipping" a journal to <a href="https://en.wikipedia.org/wiki/Open_access">Open Access</a>. This is where the editors of a journal (which is presumably published by some for-profit publisher) all simultaneously quit in order to found a new open access journal with the same scope, same editorial team, and similar name to the old one.

Some recent examples I know of this happening in math -- and specifically, combinatorics -- are:

* <a href="https://alco.centre-mersenne.org/">Algebraic Combinatorics</a>, which flipped from "Journal of Algebraic Combinatorics" 
(see this <a href="https://www-users.cse.umn.edu/~reiner/AlgebraicCombinatricsPressRelease.pdf">press release</a>, <a href="https://www.insidehighered.com/news/2017/07/31/math-journal-editors-resign-start-rival-open-access-journal">Inside Higher Ed article</a>, <a href="http://www.ems-ph.org/journals/show_pdf.php?issn=1027-488X&vol=9&iss=109&rank=9">Europ. Math. Soc. newsletter article</a>)
* <a href="http://combinatorial-theory.org/">Combinatorial Theory</a>, which flipped from "Journal of Combinatorial Theory, Series A" (see this <a href="https://osc.universityofcalifornia.edu/2020/12/combinatorial-theory-launches/">press release</a>)