Graylog looks like a good competitor. Certainly won't scale as well, but I've had good experience with it.
I am nervous about how clickhouse is going to monetize, whenever they decide to turn on the revenue spigot.
And since clickhouse is open source, we hope that people will stop giving their security data to vendors who then charge you rent for it. I think the future is writing this data to clickhouse, but also our customer's clickhouses