I've done:
update-alternatives --set x-terminal-emulator /usr/bin/xterm
... and the symbolic link in /etc/alternatives got changed. But when I
do "open in terminal" in nautilus, then it's still the GNOME-Terminal.
I see; I didn't realise Nautilus still had that feature. I thought I'd just found a "hidden" option for this in dconf, but the schema for "org.gnome.desktop.default-applications.terminal" says "DEPRECATED: This key is deprecated and ignored. The default terminal is handled in GIO." I Googled a bit more, and there are two problems: 1. GIO has a hardwired list of terminals to try. 2. Nautilus doesn't use GIO anyway; this feature is provided by a plugin which uses gnome-terminal's dbus interface and won't work with anything else.
If you wanted to use Tilix instead, you're in luck, because that apparently provides a similar extension.
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