Why in the world would you expect to "hear back" on an acknowledgment of grief? That is a very odd expectation. Do some reading about being supportive during grief.

Is there even going to be a wake/service because of Covid? If there is an obituary, they often mention a preference for charitable donations.

My father just died. A few friends and family have brought food or sent flowers, and lots of condolence notes, both cards and email. Some people have made charitable donations and all of those things are very nice. Don’t expect to hear back from them especially if you aren’t close, and it isn’t necessary to send anything more.