A paper entitled “Tick-Tock- The Imminent Merger of a Supermassive Black Hole Binary” has just appeared on arXiv. The AGN identified as NSV6690 in VSX has been oscillating around mag 17-17.5 with a steadily decreasing period and they predict a supermassive black hole merger sometime in the next 3 years.(and possibly within just 100-300 days based on most recent X Ray data!) If it happens it will be the first ever observed
I don’t know know of any formal campaigns involving amateurs though the AAVSO did contact the author offering support and there are a number of observers contributing brightness measurements. Here is the thread on the AAVSO forum https://www.aavso.org/sdssj14302303nsv6690-smbh-binary-collision-candidate
I took a couple more spectra and contacted the author who though they might be showing some changes and would follow it up with some measurements of their own, though I have not heard anything since. A quick look at the AAVSO light curve does not show anything obvious.