Interesting, that IS slightly better than I expected, at least for Ethereum. So if we treat each block being found as a lottery "ticket" and that solo miner with a 5700xt on average can expect to mine a block ("win the lottery") once every 43 months....

For Ethereum:

1 block every 15 seconds

5760 blocks in a day

172800 in a month (30day avg)

7430400 blocks in a 43 month period.

So about 1 in 7 430 400 odds when solo mining. Pool highly recommended specially because Ethereum is moving away from the current system of mining long before 43 months from now!