I know its a long shot, but I was curious how often a solo miner solves a block? Probably not a topic that would freely come up by the person solving it for anonymous purposes.
It depends on what you mean by a "solo" miner. Strictly speaking a solo miner is person or company that hasn't joined a pool.
For example, Bitfury is a solo miner. They have been doing large-scale mining since the beginning. They don't advertise in the blocks that they find, but I'm sure that they find a significant fraction.
In fact, the miners that find about 30% of the blocks are unknown. I'm sure that there are many solo miners in that group, though they are probably all large-scale operations.
Anyway the math is simple. The total hash rate is about 170 million TH/s. One S19 Pro at 110 TH/s will find a block on average once every 170,000,000 / 110 / 6 / 24 / 365.25 = 29 years. Note that this is the same whether you mine solo or in a pool. If you want to average 1 block a year, you will need 29 S19 Pros.