FTR, the issue mentioned is issue42225.

msg380227 still applies for me (with Tk 8.6.11), with segfaults when I try to preview the font. For some reason, however, the segfault appears to be when we're closing the options window:

Python 3.9.6 (default, Jun 30 2021, 10:22:16) 
[GCC 11.1.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import faulthandler
>>> faulthandler.enable()
>>> import idlelib.idle
Fatal Python error: Segmentation fault

Current thread 0x00007f0ca44c7740 (most recent call first):
  File "/usr/lib/python3.9/tkinter/__init__.py", line 2580 in destroy
  File "/usr/lib/python3.9/tkinter/__init__.py", line 2579 in destroy
  File "/usr/lib/python3.9/tkinter/__init__.py", line 2579 in destroy
  File "/usr/lib/python3.9/tkinter/__init__.py", line 2579 in destroy
  File "/usr/lib/python3.9/tkinter/__init__.py", line 2579 in destroy
  File "/usr/lib/python3.9/tkinter/__init__.py", line 2579 in destroy
  File "/usr/lib/python3.9/tkinter/__init__.py", line 2579 in destroy
  File "/usr/lib/python3.9/idlelib/configdialog.py", line 199 in destroy
  File "/usr/lib/python3.9/idlelib/configdialog.py", line 177 in ok
  File "/usr/lib/python3.9/tkinter/__init__.py", line 1892 in __call__
  File "/usr/lib/python3.9/tkinter/__init__.py", line 696 in wait_window
  File "/usr/lib/python3.9/idlelib/configdialog.py", line 94 in __init__
  File "/usr/lib/python3.9/idlelib/editor.py", line 583 in config_dialog
  File "/usr/lib/python3.9/tkinter/__init__.py", line 1892 in __call__
  File "/usr/lib/python3.9/tkinter/__init__.py", line 1858 in event_generate
  File "/usr/lib/python3.9/idlelib/editor.py", line 1185 in command
  File "/usr/lib/python3.9/tkinter/__init__.py", line 1892 in __call__
  File "/usr/lib/python3.9/tkinter/__init__.py", line 1429 in mainloop
  File "/usr/lib/python3.9/idlelib/pyshell.py", line 1572 in main
  File "/usr/lib/python3.9/idlelib/idle.py", line 14 in <module>
  File "<frozen importlib._bootstrap>", line 228 in _call_with_frames_removed
  File "<frozen importlib._bootstrap_external>", line 850 in exec_module
  File "<frozen importlib._bootstrap>", line 680 in _load_unlocked
  File "<frozen importlib._bootstrap>", line 986 in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 1007 in _find_and_load
  File "<stdin>", line 1 in <module>
fish: Job 1, 'python' terminated by signal SIGSEGV (Address boundary error)

I do not experience any problems loading the IDLE preferences page. I will look into whether I can reproduce the problem described on Windows.