With a time machine backup, you could revert. If you had a 'full
system clone' -- you could just restart in the older full macOS X.
Helps before you consider an upgrade to a new mac OS that the
third-party software makers too may be slow on the uptake. And
drivers for third-party devices generally drive people a little nutty.
{My latest Mac OS is 10.9.5; with El Capitan holding in app folder.}
There may be more information or an older version available to
if online versions aren't suitable. -- A QB16 is ready for Sierra.
As some users do not wish to subscribe to monthly fees, to be
able to keep the older software running a little while longer helps.
The retail QB desktop version had been reduced for a limited time;
($200?) I'd read about it a few days ago. Still not inexpensive though.
Sorry that you've found issue with Upgrade to an all new system.
Some of these appear to imply 'Update' but actually are fully new.
Expect the inconvenient - then be surprised - if all goes smoothly. 😉