ffmpeg concat list of videos keeping aspect ratio 16:9 for 1080p output

Question

I have looked through the internet for 1 hr now and there are a lot of answers but none works :((

So i have a folder with x amount of videos (.mp4) which have different aspect ratios (4:3, 16:9, 1:3) and so on. I want them all to be concat within a 1080p canvas. I tried all commands i could find but none worked.

my text file creation using CMD: for %i in (*.mp4) do @echo file '%i') > mylist.txt

content of text file:

file 'dave.mp4'
file 'harry.mp4'
file 'lisa.mp4'
file 'john.mp4'
file 'bill.mp4'
file 'hans.mp4'

Now I found many ffmpeg commands, the only one that worked was this but this automaticatlly takes the first videos resolution and merges all vids resulting in a black screen for most of the videos:

ffmpeg -f concat -safe 0 -i mylist.txt -c copy output.mp4

I read so many complicated commands that I feel dizzy now, isn't here a way to simply just add a parameter of the canvas size (my desired resolution would be 1920x1080 which is 16:9 and automatically fit all videos proportionally within that frame.

can someone PLEASE help me?

Sinceraly Gram