Hello, I just had to start with a fresh install of Anaconda and I found that Pyfda failed with the Pyqt not found issue. However I found an easy work around.

The method that failed was-
Created Pyfda environment using Anaconda Navigator Gui. This forces you to choose a version of python to preinstall and defaults to 3.12.9
Then I used the command line as per your readme-
conda install --channel=conda-forge pyfda

Pyfdax won't run.

Traceback (most recent call last):
File "C:\ProgramData\anaconda3\envs\pyfda_bad\Scripts\pyfdax-script.py", line 5, in
from pyfda.pyfdax import main
File "C:\ProgramData\anaconda3\envs\pyfda_bad\Lib\site-packages\pyfda\pyfdax.py", line 23, in
import pyfda.pyfda_rc as rc
File "C:\ProgramData\anaconda3\envs\pyfda_bad\Lib\site-packages\pyfda\pyfda_rc.py", line 19, in
from pyfda import qrc_resources # contains all icons
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\ProgramData\anaconda3\envs\pyfda_bad\Lib\site-packages\pyfda\qrc_resources.py", line 9, in
from PyQt5 import QtCore
ModuleNotFoundError: No module named 'PyQt5'

conda list qt
gives the following

Name Version Build Channel
pyqt 6.7.1 py312h5da7b33_0
pyqt6-sip 13.9.1 py312h827c3e9_0
qtbase 6.7.2 h0804d20_1
qtdeclarative 6.7.2 h5da7b33_0
qtsvg 6.7.2 hf2fb9eb_0
qttools 6.7.2 h0de5f00_0
qtwebchannel 6.7.2 h5da7b33_0
qtwebsockets 6.7.2 h5da7b33_0

If however the pyfda environment is created from a terminal window using the command line interface then everything is okay-

conda create --name pyfda
conda install --channel=conda-forge pyfda

At this stage pyfdax runs fine.

For information the following libraries are present when the environment is created like this

Name Version Build Channel
pyqt 5.15.10 py313h5da7b33_1
pyqt5-sip 12.13.0 py313h827c3e9_1
qt-main 5.15.15 h9151539_2 conda-forge