I have been running Debian 13 for a while now, but I still had one system on Debian 12. Last week I upgraded it to version 13

To do this I followed the steps in How to Upgrade Debian 12 Bookworm to Debian 13 Trixie. This worked quite well. It was definitely smoother than my experience of upgrading version 11 to 12. There were no problems with grub this time. I did get a warning about a couple directories, e.g. /usr/sbin, being missing from $PATH. This may be because I was doing everything with an su from my usual user account and still had that account’s path. I ignored the message and everything was fine.

Next step: Upgrade Ubuntu 24.04 (which I am using right now) to 26.04. I will wait for Canonical to publish an official procedure for this, which IIRC is supposed to happen in July.