6I25 --recover

I do believe that my problems were related to the mesaflash version that is packaged with the Buster LinuxCNC ISO. It did not behave properly with the Mesa 6i25 card. After downloading the version from GitHub, and compiling it, the 6i15 card works as expected, and I could then isolate the ethernet problem (caused by NetworkManager).

Thank you, Peter & Tommy for your hand-holding through this adventure!