Grub seems a lot more complicated now than it used to be a few years
ago when I last upgraded Debian from one release to another.

My usual procedure is to copy the system to new partitions (adjusting
the size according to what I actually guess I might need),
editig the copied /etc/fstab, making sure the old and new systems boot
properly and mount the right partitions, and then upgrading the new
one.

That way I have a fallback in case something goes wrong (and in about
1 in 3 upgrades it does).

I would edit the boot configuration to make sure the new system was
properly represented.

But grub seems to have been massively complexified.

I suppose I *could* edit /boot/grub/grub.cfg and risk getting
overwritten. And, yes, keep a copy in case it *is* overwritten.

But what's the recommmended way to do this?

-- hendrik