[ 24.436673] QDBusConnection[2697]: segfault at 7f91b1c8da68 ip 00007f91be8fa76d sp 00007f91b8ca9a00 error 4 in libQt5Core.so.5.15.9[7f91be697000+316000] likely on CPU 11 (core 20, socket 0)
Also if you ask for help, you are expected to do some of the work yourself, and mention what you did. Otherwise, you run the risk of being considered a help vampire, and invite moderate application of garlic.
For segfaults, the minimum information necessary are:
When does the crash happen? In response to which user action?
Stack trace including debug symbols. After obtaining the symbols, run coredumpctl to find the process id of the crashed process and then coredumpctl gdb <pid> in which you enter bt command.
Well, from all the context you provided, it looks the same to me. So unless you have some reason to think it is a different issue that you have not shared, I would assume it is the same issue.
General procedure for debugging crashes is getting a stack trace to find out what part of a program is responsible. That is not really specific to NixOS (see e.g. Arch Linux or Fedora) and we can help guide you through the process if you need more details.