https://www.softmaker.com/en/softmaker-office - Softmaker support Mojave and later. And it is the only Microsoft Office clone that does a very good job of retaining page layout of Microsoft Word.
Older versions of Office do support Big Sur, but you would need to find someone who has the older version willing to part with the license.
iCloud offers Pages App on the web on your Apple ID, and http://www.office.com/ offers a web version of Microsoft Word, neither of which are quite as good as Softmaker.
If you maintained a clone backup of an older installation of Office on a hard drive you still have, you might be able to restore that clone which would include all the license preferences of that older version of Office.