I would not say support is dead, but fixes will come few and far between. The P3a/XL and OP5T are far better supported.
The OP6/T does have one major advantage - mainline linux support. I am running mine on gnome mobile via PostMarket. There have been some recent bugs because of recent inprovements, but the postmarket build runs better than the UT build for the device. Recently, gps and sensors have been made at least partially functional, and VoLTE is being worked on. There is effort to get the camera going but it's a lower priority. I think it is quite possible it will be the first fully functional mainlined android phone in a while. Your other option would be the Pinephones of course. They are VoLTE functional now, but have other bugs / pain points.
If you are looking for "just works", then the P3a/XL or OP5T will fit nicely. I do not have a Volla, nor Fairphone to compare with, so I will defer to someone who does.