Hi, if the target is seen as read-only by Etcher it means that the OS sees that as read-only for some reason. The part that gets the drive data for macOS is here for example drivelist/list.mm at fcdc5ab0b9eb74579b7ab49e970f0e052e73b7b3 · balena-io-modules/drivelist · GitHub and we then check this value Apple Developer Documentation .
I don’t know why this could be the case just for writing an image, but it seems like either that operation sets the target to read-only or (more likely in my opinion) the card reader/media that you use to plug the card (the adapter, in this case) could have some issues.
I would try with a different reader and adapter, unfortunately there’s not much we can do if the OS sees the target as read-only.