I use an Outlook.com account to save Appointments.
The glitch that caused Outlook.com Appointments to turn into Meetings has been fixed for Version 15.20.906.0 of Outlook Desktop App. Version 15.20.906.0 was included with the Office 365 subscription that I purchased for my laptop. Now that glitch has
been fixed, Appointments do not convert into Meetings when I can create, change, or view Appointments using Outlook Desktop App, Outlook for iOS, or Apple's Calendar App. Many thanks to Microsoft's Outlook Team for fixing the glitch. For tips on using Outlook
for calendaring, see below for link to excerpt from Microsoft Press book on Outlook 2016 Step by Step:
MANAGE SCHEDULING IN MICROSOFT OUTLOOK 2016
https://www.microsoftpressstore.com/articles/article.aspx?p=2477121