Of the 10 wikiversity wikis that have Tidy enabled, el and en are getting switched over to Remex March 13th as part of T188010: Enable RemexHTML on additional wikis with < 25 errors in all high priority categories.
Of the other 8 (ar, cs, de, fr, it, ru, sl, sv), except for dewikiversity, the other 7 wikiversities have some categories over 25 linter errors but fewer than 100 in all cases.
dewikiversity might need more fixes, but the html5-misnesting errors are not serious since in all the scenarios I looked at, the misnesting is coming from a span that has no CSS and hence won't have any real rendering impact.
I plan to switch the 8 wikiversity wikis to RemexHtml the week of March 21st.