Seriously, just use Office 365. Otherwise you'll forever be dealing with a constant low grade stream of interoperability glitches.
Yes, file formats are usually interchangeable. No, that interchangeability is not perfect, especially once you get away from word processing and into spreadsheets and presentations.
The majority of people your partner has to work with outside of their charity will be using Office so these small issues will constantly cause friction and frustration.
Does your partner want to waste time on those issues or do they want to focus their energy on the good work of the charity?
And, since we're talking about a charity, O365 is probably available at a reduced price, or even free.
Yes, file formats are usually interchangeable. No, that interchangeability is not perfect, especially once you get away from word processing and into spreadsheets and presentations.
The majority of people your partner has to work with outside of their charity will be using Office so these small issues will constantly cause friction and frustration.
Does your partner want to waste time on those issues or do they want to focus their energy on the good work of the charity?
And, since we're talking about a charity, O365 is probably available at a reduced price, or even free.