@william For others reading, upgrade instructions are here: https://soapbox.pub/install/
There will be some downtime. How much depends on how old your installation is. Do you have the ability to Edit posts already? If so, downtime will be brief. If no, you may want to wait until after Christmas, and be prepared to run pg_repack after: https://gitlab.com/soapbox-pub/rebased/-/snippets/2463995
Regardless, you can upgrade just the frontend now, which will be no problem and has no downtime.