Viewing md files: Switch between preview and plain text view

Hi
When editing a .md file, is there a way for a user to switch between preview and plain-text view?
That functionnality was available through the Markdown editor app, but of course every app got broken with NC28, so now a very basic functionnality isn’t available anymore and the NC app store has more apps that don’t work anymore than actual up-to-date apps.
I can’t understand how a piece of software such as Nextcloud doesn’t have any possibility to open and edit plain text files resgardless of their file extension.
Any clues ?