I can remember testing libre office in the browser many years ago, seems like that project was frozen in 2020 as others external projects emerged. The wiki has a guide for docker:
https://wiki.documentfoundation.org/Development/LibreOffice_...
the link you refer to talks about collabora and allotropia. the first is what powers Nextcloud Office/Collabora Office online and mobile apps (using coolwsd). the latter is allotropia, who is behind Zeta that is mentioned here. both have a slightly different approach to how this works. as i understand it, all of this is upstream and not really frozen; perhaps that page needs an update?
Note: "LibreOffice Online is not intended as a standalone software. His goal is, instead, to be integrated with other tools to edit their documents." ... while Zeta and Collabora are standalone.
It wasn't frozen, Collabora were the ones doing the work and so they have largely hosted and developed LibreOffice Online.
(same thought here; just didn't want to sound harsh)
The idea of LOOL (LibreOffice OnLine) is to be an embeddable component; we have used it before on a Moodle site. And this is the same for COOL (Collabora Office OnLine), which is used by Nextcloud Office (as components called COOLWSD, and LOKit).