So I’ve bought the nanokvm-usb. Why:

• I needed it quickly and was available
• the idea of going through another server for secutiry seemed better: I control the updates and security fixes
• well tested on the internet

the product itself costed around 50€ and I found a used mini pc with wireless connection for 25€

it was easy to install, works fine and is of good quality

So I got it working by buying an Terra MT47 modulator !

thanks to @mayasynth@eldritch.cafe and her advices !

So what is happening is quite simple:

I AM FRENCH

which is considered bad when using old TVs. Why ?

Because we use L and L’ bandes when most modulator are using B/G or things like that
So, that won’t work properly.