Hey Yannick,
Here is one solution that could help you get around the plank limitation problem:
Quarantine Weighted Pushup.jpg
This is what I started doing during the lockdown last March. You can get a weight vest and do pushups with books under your hands to let you get the full range of motion in. The weight vest is strapped to your chest, so your ability to plank is less of a limiting factor. I got my kids to sit on my back to add even more weight when the weight vest wasn't enough. The problem with kids is that they're squirmy.