For what it's worth, I can report a bit of additional information. First, if I make a new user account on my Pop!OS machine, the autocompletion window appears as expected in Eiffel Studio. From this, I infer that the problem is not in the machine or in the operating system or in the packages that have been installed, but somewhere in the dynamic environment of a particular user. I have not found anything promising in the environment variables or in the Pop!OS Settings interface but I'll keep looking as long as I can think of places to look. Getting Eiffel Studio running for another user account on this machine did help me find the cause of my other problem report (https://support.eiffel.com/report_detail/19868) and I am hopeful that it can help with this one as well. Second, in an attempt to see if I could provoke Eiffel Studio into giving more information about the problem with the popup autocompletion windows, I invoked ec with the options "-debug -gui -stop". Then in Eiffel Studio I opened a project (chapter 7 of A Touch of Class, to be specific) and typed "Elysee_palace." to try to invoke an autocompletion popup. As I had hoped, Eiffel Studio exited with an error message, but it does not shed much light for me. Perhaps it will mean more to you. As you can see, the message says core was dumped, but I have not located the core dump anywhere in ~/.es or in the directory from which I invoked ec (or the EIFGEN directory there). If the core dump would be helpful to you and you can give me a hint about where to find it, I'll be happy to retrieve it and pass it along. $ ec -debug -gui -stop ec: PANIC: Unexpected harmful signal (Segmentation fault) ... ec: system execution failed. Following is the set of recorded exceptions. NB: The raised panic may have induced completely inconsistent information: ******************************** Thread exception ***************************** In thread Root thread 0x0 (thread id) ******************************************************************************* ------------------------------------------------------------------------------- Class / Object Routine Nature of exception Effect ------------------------------------------------------------------------------- FEATURE_SERVER retrieve_all <00007F7043B7BA28> (From ISE_SERVER) I/O error. Fail ------------------------------------------------------------------------------- FEATURE_SERVER retrieve_all <00007F7043B7BA28> (From ISE_SERVER) Routine failure. Fail ------------------------------------------------------------------------------- FEATURE_SERVER item @9 <00007F7043B7BA28> (From COMPILER_SERVER) Routine failure. Fail ------------------------------------------------------------------------------- FEATURE_SERVER item @3 Unexpected harmful signal (Segmentation fault): <00007F7043B7BA28> (From COMPILER_SERVER) Eiffel run-time panic. Panic ------------------------------------------------------------------------------- ec: dumping core to generate debugging information... ec: PANIC CASCADE: Unexpected harmful signal (Segmentation fault) -- Giving up... Third, and possibly unrelated, I note that the bash window from which I invoke estudio often receives warnings from GTK. An earlier (short) session in this userid, for example, produced the following in the shell window. cmsmcq@gemma:/home/sw/Traffic/Traffic3-master/example/07_control$ estudio (ec:36120): GLib-CRITICAL **: 20:05:03.202: Failed to set scheduler settings: Operation not permitted (ec:36120): Gtk-WARNING **: 20:05:43.199: no trigger event for menu popup (ec:36120): Gtk-WARNING **: 20:05:43.229: no trigger event for menu popup (ec:36120): Gtk-WARNING **: 20:05:43.476: no trigger event for menu popup cmsmcq@gemma:/home/sw/Traffic/Traffic3-master/example/07_control$ I have not found any correlation between these warnings messages and my attempts to get an autocompletion window; they seem to be elicited when I open Tools / Preferences ... or perform other interactions. The "no trigger event" warnings come up frequently; the critical warning about scheduler settings comes up sometimes but not every time and I have not found a pattern. But as you can see, none of these warnings was issued in the session invoked with ec whose output is reproduced above. I hope this helps.