Installing the March update today via the factory image and fastboot (as I usually do) I found that patching and flashing boot.img as I usually do didn't work: it booted OK (albeit slower than usual), but no root.
I eventually realised that this is the release-candidate issue mentioned above, now affecting regular updates (so beware!)
After a lot of fruitless experimentation with Pixel 7 boot images etc (none of which worked), I discovered to my relief that the latest Alpha of the Magisk app does the trick fine (usual method: patch boot.img on the device and then boot from it or flash it with fastboot as normal.)
I hope this saves somebody a bit of time (and that it solves the problem for them too.)
Apparently it may not get fixed in Magisk proper, as the issue seems to be a screwup by Google.
I eventually realised that this is the release-candidate issue mentioned above, now affecting regular updates (so beware!)
After a lot of fruitless experimentation with Pixel 7 boot images etc (none of which worked), I discovered to my relief that the latest Alpha of the Magisk app does the trick fine (usual method: patch boot.img on the device and then boot from it or flash it with fastboot as normal.)
I hope this saves somebody a bit of time (and that it solves the problem for them too.)
Apparently it may not get fixed in Magisk proper, as the issue seems to be a screwup by Google.