supposedly the j-core open core (sh compatible) isnt totally dead. the main patents seem to have run out, so implementation ought be ok. but definitely havent seen what the hopeful roadmap pitched happen: https://j-core.org/roadmap.html
They haven't come around to updating the page for a while (someone lost login info or something like that) but they have a new core and some projects that use the new SH4 equivalent core. https://www.coresemi.io/
They currently seem to be in a "release tarbal" model of open source but know they ought to be in an develop on master branch in public repo model.