This has been addressed on this forum here: How to get data attribute in Custom JavaScript variable? - #5 by ulli_s
And a nice article can be found also here: https://www.mikkopiippo.com/matomo-analytics-event-tracking-using-data-attributes/
In addition to above it seems tomper00 made a very nice JS script:
Data attribute tracking is a technich that allows you to just set meta data in your code and from that automatically send event tracking to Matomo without having to add triggers, tags and variables in the TagManager