+1
From an order of magnitude perspective, the max is terabytes. No "normal" users are dealing with petabytes. And if you are dealing with petabytes, you're not using some random poster's program from reddit.
For a concrete cap, I'd say 256 tebibytes...
I love my Turris Omnia!
I got the one with the WiFi 6 card. The cool thing is that you can easily open it up and replace parts.
I run the upstream OpenWRT rather than the customized version by Turris. They are good about submitting patches upstream.