It’s probably because of resistFingerprinting in about:config.

Unfortunately sites need to use them or someone similar to not get attacked to shit by AI bots. Websites could turn off the challenges (which are that captcha) so Cloudflare just absorbs DDoS attacks, then use the open source Cap inside the site on things like the log in page and comments instead.

Sailfish OS has proprietary components and they were working with Russia, so I don’t trust them.

It is a fork of LineageOS with Murena bloatware and very late security updates. Lineage (best for wide device support) and Graphene (best for security and actively fixing compatibility with apps) are much better choices.

You should deploy standard Firefox and use group policies to lock it down.