I confess that I am on the low end of the grub learning curve but I need to make one debian system duel-boot with a different debian version. One version is debian wheezy which I want to keep because there are some PIC microcontroller development tools that make just fine in wheezy but the make process blows sky high with stretch or buster so the answer is to make a wheezy partition and a newest such as buster partition and select one of these two at boot time.
I absolutely hate what I call "press and pray" in which the silent world prevails and you count button presses in the silence and hope and pray that nothing weird happens. Failing speech, I know grub can be configured to work through a serial port if one exists at the time grub is needed. Is there a good document anywhere dealing with all these issues? This very Summer marks 30 years that I have been working with unix-like systems so like lots of skill-based systems, I am familiar with the feel of unix but grub has always been that mystery thing that you automatically say yes to when installing debian or freebsd. Now, I want to hopefully do something useful with it. The less extra hardware needed to read grub's output, the better off we are and I am aware that very little resources are operational when grub is working. Thanks Martin McCormick