I tried Fldigi on my Raspberry Pi 5 with the last version of Raspberry Pi OS (bookworm).
This version use Wayland (like the Ubuntu version you tried) as default instead of X11.
From the release notes:
* Desktop now runs on the Wayfire Wayland compositing window manager on Raspberry Pi 4 and 5 platforms; on X11 using the openbox window manager on older platforms
* lxpanel replaced with new wf-panel-pi application when running Wayland; existing lxpanel plugins migrated; gpu performance and power plugins added
I also noticed a slow response when the waterfall was drawing something and the Xwayland process was using a lot of resources.
I tried switching to X11 using the Advanced settings in the raspi-config tool and Fldigi was happy again.
I suppose that the Wayland implementation is too new.
73
Haris
SV1GRB
Haris SV1GRB