Took about 30 secs for me (5 yr old intel cpu). Looked like there was a progress bar, but it didn't progress. Maybe the difficulty varies depending on IP address?

Anubis has config for that: https://anubis.techaro.lol/docs/admin/policies#request-weigh...

It's up to the site admin to configure it that way, but it's possible some IP ranges/user agents are more often used by bots and therefore have an increased weight.

For old browsers there's also an option to use meta refresh instead of JS (https://anubis.techaro.lol/docs/admin/configuration/challeng...) but that's quite a recent addition and not enabled by default.

> Maybe the difficulty varies depending on IP address?

I'm currently roaming in Finland with a Spanish SIM so would have expected the opposite in that case.

my i5-6200U with firefox/linux is about 10 years old. I used a variety of add blocking and fingerprint blocking techniques. Cloudflare often complains and blocks me.

This page loaded pretty much instantly (certainly in the time it took to switch to the background tab I loaded in). But then ffmpeg is written by old school engineers with old school ways of working. Their social media accounts are a hilarity of trolling worthy of slashdot in its peak.