@stephen.smith If you really must use the web app, see my answer here Joplin web app cannot sync with joplin server anymore? - #4 by mrjo118 for an easy (and free) way to host the web app yourself. You'll need to do upgrades manually, but when you want to upgrade, you only need to press a couple of buttons and the rest is automated.
Also going to mention this because if you never used the web app before other sync providers were dropped, you might not realised this. Joplin has an offline first architecture unlike Evernote / OneNote / Apple Notes. So even if you do setup sync successfully on the web app, you're not going to have instant access to your notes. On a new device, you're going to need to do a full sync of all your notes just like with the mobile or desktop app, so if you were expecting instant access to your notes on a guest device, Joplin does not support this feature full stop.