I understand an online version of MS Excel is needed for Tiller.
I’m curious if there are any plans to support the PC based MS Excel?
Google Sheets vs Microsoft Excel
Our Excel add-in only works for Excel installed via a Microsoft 365 subscription or Excel Online.
The modern versions (those available through an M365 subscription) of the desktop version of Microsoft Excel are supported on Windows and MacOS.
Yeah, I understand that m365 is what works today per the help article, but I’m referring to MS Office 2019/2021/2024 (no m365). And not if it works today, but perhaps down-the-road.
hi @Mark.S - we don’t have plans for backwards compatibility support on those version of Microsoft Excel. We will only ever support Microsoft Excel installed from Microsoft 365.
MS Office 2024 is in the future, though.
Correct, but if it’s not installed from Microsoft 365 it won’t be supported.
Why is that, the technical reason?
I know many software vendors only support their software on specified configurations because that’s where it’s been tested. The software may still run on other configurations, but the vendor can’t confirm it will run as intended since it hasn’t gone through testing on the many possible configurations available. In the case of Tiller, I suspect as long as the version you are running can install the add-on(s) and can understand the functions in use in the templates (eg. XLOOKUP, LAMBDA, etc) then it will probably work fine, but Tiller likely won’t ‘guarantee’ everything will work fine for you since it hasn’t been fully tested in that environment. The more Community Solutions templates you add, the more likely you’ll need a newer version as those that develop community templates (like me) are likely to use the latest available functions to improve the capabilities of their templates.
Good point. e.g. XLOOKUP was introduced with 2021 Excel, so that would break in 2019 Excel.
From a Tiller strategy perspective, only supporting M365 versions allows us to more easily stay current with the APIs and technology offered from Microsoft. Things start to get out of sync in what’s available in their API after a while between a standalone version and the M365 version. @jpfieber’s response is accurate too 
2024 might work for a while, but the best bet for it to always work is to use a M365 version and we can’t support/help you if you’re not using that version.