Plots look wrong or they are not shown at all in octave. Problem is related to graphics toolkits 'qt' (the default one) and 'fltk'. It happens in when using octave version installable from PureOS amber repositories (4.4.1) but also the latest version through flatpak and the development version from Octave repository. It does not happen in Debian 10 (tested in a virtual machine).
Example to reproduce:
$ octave
[...]
octave:1> x=0:0.1:10; y=sin(x);
octave:2> plot(x,y, '+r')
I include a screenshot of an example of correct behavior in Debian 10 and what is shown in PureOS amber.
{F411471}
{F411470}
As a workaround, 'gnuplot' toolkit can be used
```
graphics_toolkit("gnuplot")
```
and plots seem to be displayed correctly.
I am available to help if it is needed.