Eve disconnects after ~1 min of idle time

Using linux, ubuntu 19.10, nvidia gtx770 (driver version 440.26), wine 4.19 staging, dxvk 1.44,
I get disconnected after ~1 minute of inactivity in station or in space. The chat server disconnects and re-connects endlessly every few seconds.
The loglite log is here: https://pastebin.com/ef6FNXvh (first error: module svc, channel michelle, “Failed to get a valid ballpark in time after trying 30 times”). I used the launcher’s network diagnostics tool, and the results are here: https://pastebin.com/7FY3AgMb
I checked with my ISP and they say they see nothing on their end. They tried giving me a private IP, but this did not help. They also changed my router to a newer model, but to no avail.
I cannot file a ticket, because CCP does not officially support linux, but the problem might be outside my computer, and if so I want to find out where it is.
How can I diagnose this and find out where my problem is?