Observer font sizes on HiDPI displayer

Running Ubuntu 20.04 and i3 as my window manager, and I'm struggling
with Observer ending up with tiny text. This is on a Dell XPS 13 with a
HiDPI display. Clearly I'm making things a bit difficult for myself, so
wondering if I've missed something...

I can set the environment variable GDK_DPI_SCALE to (say) 1.6 and that
helps to a certain extent. The text on the 'System' page is much more
readable.

I can set another (undocumented?) environment variable OBSERVER_SCALE
to (say) 3 and now the 'Load Charts' page is readable as are the graphs
on the 'Memory Allocator' page. However the list of allocators at the
bottom is very small and hard to read. Ditto the process list on the
'Processes' page. In fact any text that is generated from a list.

I've never played with wx much but I had a quick look at the code which
is how I found the OBSERVER_SCALE trick. However, I don't grok it all
yet. For instance, I'm suprised that GDK_DPI_SCALE affects the fonts on
one page, but not on others - so clearly some different drawing
mechanism is at play.

Anyone else have this issue and found a solution?

Cheers
Rick