I found updating my plugins to work with Moodle 5 was fairly straightforward. Due to a change in API, I have had to create two versions of my QBank Bulk Tagging plugins as the question bank has changed quite a bit, and after the latest version I will only support Moodle 5 onwards.
https://moodle.org/plugins/qbank_bulktags
https://moodle.org/plugins/qbank_bulktags