This is the way. I had a story in WhatsApp for 3 months every day with a picture that I am going to fully switch to Signal and Threema and won’t be available over WhatsApp anymore. As you said, people who want something from me will have to jump over their shadow and write me over one of those. And it absolutely worked, took some time, but it worked. Some people even have signal installed only to text me. The rest just calls or sends SMS. I am from Europe btw. and it worked even though WhatsApp is so strongly used over here.