I am certainly not one to defend the new ansible docs, but part of the woes that you're describing are due to the fact they just doubled down on `ansible-galaxy install` based setups, meaning there isn't "an answer" to what filters are available in ansible

The authoritative answer to what filters are currently available in your distribution is by running `ansible-doc -t filter --list` which does include a summary line, although for some of them it's "geez, thanks" just like any open source collection of disparate modules glued together

I used to actually build the ansible docs locally with singlehtml because I despised that chopped-up view, but now that they're all "galaxy all the things" it's practically useless again (although I will also say that building it locally and eliding all their tracking bullshit makes the pages load like a bazillion times faster, so ... still valuable in that way)