ffmpeg: create slideshow of unknown number of images with transition

hope someone could help me with this. Kinda new with ffmpeg and a bit stumped.

Given an input of a set of numbered images in a folder, I want to generate a video with each image shown for 60 seconds. I would love to use a default transition between each images.

The following code, correctly generates an mp4 without transitions:

ffmpeg -framerate 1/60 -pattern_type glob -i "*.png" -vcodec libx264 \
-pix_fmt yuv420p -r 30 -threads 4 -crf 25 -refs 1 -bf 0 -coder 0 -g 25 \
-keyint_min 15 -movflags +faststart no_audio_output.mp4

But when I try to add a default transition (supported in the version of ffmpeg I’m using that is the 5.1):

ffmpeg -framerate 1/60 -pattern_type glob -i "WC*.png" -filter_complex 
xfade=transition=circleopen:duration=5:offset=55 -vcodec libx264 \
-pix_fmt yuv420p -r 30 -threads 4 -crf 25 -refs 1 -bf 0 -coder 0 -g 25 \
-keyint_min 15 -movflags +faststart no_audio_output.mp4

I have as error:

Cannot find a matching stream for unlabeled input pad 1 on filter Parsed_xfade_0

I googled a lot but still the solution is unclear. All the examples I found have been designed to deal with a slideshow/input with a define number of pieces while in my case the folder could contain any number of images.

Thanks all for your help!