There won’t be a March update because, just like 2a Plus and NP1, the CMF Phone is on an evenly month update cycle: February, April, June,…
Since Nothing usually only does bimonthly security updates, the next one will be April and they are typically releasing their security updates within the second half of a month.
The last update was for February released on Feb 17th, so the next one will be April and should be released within the next two weeks.