You just solve it as per the blog post, because it’s trivial to solve, as your browser is literally doing so in a slow language on a potentially slow CPU. It’s only solving 5 digits of the hash by default.
If a phone running JavaScript in the browser has to be able to solve it you can’t just crank up the complexity. Real humans will only wait tens of seconds, if that, before giving up.
It will obviously depend heavily on the type of bot crawling, but that is not hard coordination for harvesting data for LLM’s, as they will already have strategies to prevent nodes all crawling the same thing - a simple valkey cache can store a solved JWT.
The author demonstrated that the challenge can be solved in 17ms however, and that is only necessary once every 7 days per site. They need less than a second of compute time, per site, to be able to send unlimited requests 365 days a year.
The deterrent might work temporarily until the challenge pattern is recognised, but there’s no actual protection here, just obscurity. The downside is real however for the user on an old phone that must wait 30 seconds, or like the blogger, a user of a text browser not running JavaScript. The very need to support an old phone is what defeats this approach based on compute power, as it’s always a trivial amount for the data center.
I picked zoho.com free tier, with an eu.org domain after scanning through a set of different options. No marketing appended to emails and only throttles on excessive sending instead of hard limits. Each service sends from its own address.
purelymail.com was my backup paid option if the free plans were no good, with the advanced pricing and low usage the cost would be miniscule.