Instead of this:

  T *item = &this->shared_mem_region
                 ->entities[this->shared_mem_region->consumer_position];
  this->shared_mem_region->consumer_position++;
  this->shared_mem_region->consumer_position %= this->slots;

you can do this.

  uint64_t mask = slot_count - 1;  // all 1's in binary

  item = &slots[ pos & mask ];

  pos ++;

i.e. you can replace a division / modulo with a bitwise AND, saving a bit of computation. This requires that the size of the ringbuffer is a power of two.

What's more, you get to use sequence numbers over the full range of e.g. uint64_t. Wraparound is automatic. You can easily subtract two sequence numbers, this will work without a problem even accounting for wraparound. And you won't have to deal with stupid problems like having to leave one empty slot in the buffer because you would otherwise not be able to discern a full buffer from an empty one.

Naturally, you'll still want to be careful that the window of "live" sequence numbers never exceeds the size of your ringbuffer "window".