I believe this used to work with e.g. something like https://lemmy.ml/post/2401677@feddit.org (assuming federation works and is current and all that).

This URL format no longer seems to work, is there a new/different endpoint to achieve the same?

I've found that I can use https://feddit.org/post/2401677 as a search term on https://lemmy.ml/search but putting together the appropriate URL (https://lemmy.ml/search?q=https%3A%2F%2Ffeddit.org%2Fpost%2F2401677&type=All&listingType=All&page=1&sort=TopAll) with a bookmarklet does not quite work - it comes up showing "no results", but I can click on "Search" again without changing anything and the same page / very same URL loads again with the post I'm looking for as the only search result. This link in this post also shows this exact behavior for me.

Is there any convenient way at all to achieve this - something I can click once, like a bookmarklet?

For reference, here's my half-working one:

javascript:(function() {const myInst="https://lemmy.ml/";let currUrl=window.location.toString();let newUrl=myInst+"search?q="+encodeURIComponent(currUrl)+"&type=All&listingType=All&page=1&sort=TopAll";window.location=newUrl;})()