Seems like the recent update of Dokuwiki broke some plugins (and other stuff).
I will look into this.
Edit: Fixed.
The cache needed to be purged.
Should you find more pages like this, you can try to simply add ?purge=true to the adress of the page. If this doesn't fix the issue, please let me know.
tmomas, thanks.
Super. "tabbox" syntax in pages is working again as expected. Some just by reloading pages in web-browser, some by adding ?purge=true to the address of the page as you suggested.
I investigated some more.
Quite a lot of plugins are affected by the latest changes to dokuwiki.
In the OpenWrt wiki at least the datatables + columns plugin are affected.
I was getting annoyed by a non-working wiki and have upgraded to dokuwiki master (which includes https://github.com/splitbrain/dokuwiki/pull/3132 and which seems to solve all problems with plugins).
Should there still be pages with seemingly non-working plugin output, simply add ?purge=true to the adress of the page.
If that doesn't fix the issue, please let me know.