Microsoft is pretty good at giving away cheap or free licences to charities.
Whether you personally are a "Being a die-hard OSS geek" is as irrelevant
as if you are gay.
Unless you plan to stick around and volunteer for the next decade or
more, or you have a steady supply of "Being a die-hard OSS geek"
volunteers lined up replace each other, dont be an ass and land the
charity in deeper problems.
Are you donating cloud servers for them to use to host the
MySql plus python for the next decade with built in support?
Or do you intend to install it on one of their machines, maybe
with Linux on it, and install the app via docker?
You want a solution that is as easy for non computer people
to use but also to MAINTAIN, to MOVE, to UPDATE.
Access has a lot of issues, but even a volunteer with
little experience can move an access file. if required,
and fill out forms.
If the charity is lucky they will land another geek who
can add some fields to a form and make a new report
something like that.
In fact, a lot of the user would probably prefer to track
the whole thing in a spreadsheet, because its something
Having your super duper optimized Mongo db Python
node.js application be super fast, and really OSS, aint
gonna be a good thing when Bob takes over from you
and they need two new reports.
For this kind of charity work KISS: Keep it simple Stupid.
and KIRSS Keep it real simple stupid.
You need to spend more time writing a user manual and
documentation that will live on after you are gone that will
be needed and loved by all than you do inventing a tech
stack and writing software to do a job Access does ok.
Want support for Access? Easy to get.
Want someone to support your Mongo, Python, node.js
application. Hard to get.
Access, probably wont cost them anything
Access, lots of easy ways to get support
Access, its in MS Office, kinda looks a bit like Office, People like Office.
Access, super easy to export data into Excel
Access, built in report generator that might be used by a power user.
Access, made for this use case.
Personally I dont want to touch Access with a ten foot pole,
and consider it evil, but if I am trying to help a charity get
going, raise money and general do good by them, for this
work Access is the best option, even if I have to humiliate
myself to set it up. Its not about you living your OSS dream,
its about helping those in need.