The dividends were omitted income on the 1040's that were filed for the years they were paid.  Taxpayer might not have received the 1099's but IRS got them and must have figured it wasn't worth asking about.  The sale of stock by the state should also have been reported on a 1040 (or maybe a 1041 if the taxpayer had already died) in the year it happened.  The one thing you know for sure is that it doesn't go on a 2021 return.  

Sometimes the state will provide more information if you ask for it.   Can you find the last tax return where he did report the dividends?  

If you believe in an after-life, he's looking down now and thinking, "I didn't trust any brokers, they were going to have to pry those stock certificates from my cold, dead hands."  Well, it happened.