@FredK thank you so much for the instructions. They allowed me to boot up my helios4 again.
If I may, don't buy anything ARM-based if you don't want e-waste in 5 years because there's no software support. When my helios4 finally gives up I'll get an odroid-h4+ (https://www.hardkernel.com/shop/odroid-h4-plus/) or whatever equivalent they have at that time.