For a while I’ve been working on converting the NTP charm to use charms.reactive and support chronyd on bionic. The code for this has been committed and the result is cs:ntp-29, currently released in the candidate channel.
Please note that if you’re using bionic, this will switch your NTP implementation from ntpd (which moved to universe as of bionic and no longer receives security support) to chronyd (which was included in main at bionic). Functionality should be the same with both implementations.
Please give the new version a test and let us know here or with a bug report if you notice any problems.