I would certainly keep the eMMC disabled until you get it working. The eMMC is totally unnecessary to make it work with the SD card, and this is the minimum configuration.
Please do try the power long-press. If it's currently on and locked (it does seem that way), then doing this will cause it to power off. In that case, you can power it on, and it should boot.
I have no experience with etcher, but that is the recommended tool, and should get the job done.
Please do try the power long-press. If it's currently on and locked (it does seem that way), then doing this will cause it to power off. In that case, you can power it on, and it should boot.
I have no experience with etcher, but that is the recommended tool, and should get the job done.