Form Letter from Contacts Address List for association

Welcome to all Nextclouders

Up until now I did use ownCloud/Nextcloud for:
Personal (Server, PC/Thunderbird, Android/DAVdroid): Contacts, Calendars and sharing of them and some pic/file sharing
Webmaster for a small volunteer association: pic/file sharing (simple upload/creation of galleries for a couple of users).

In one hour I have a meeting with the person responsible for the finances of the small volunteer association: he would like to know if there is a possibility to create a Central management system, in particular regarding contact management, as well as financial and other administrative activities (e.g., creation of Form Letters for all types of mailings). I know that Collabora Online integrates LibreOffice in Nextcloud but did not find anything useful with some short googling regarding this topic and I can’t install Collabora Online on my shared webhosting to try it out. I will show to my friend what I know about Nextcloud and that I will try to find out more.

I would be particularly interested if:
a) there is a possibility to extract a csv or other type of address list (postal, emails) from the Nextcloud contacts?
b) Collabora Online allows to use Write with Form Letter functions?
c) Anyone is using Nextcloud for an Association in ways like described above or if there are other more suited FOSS solutions?
Thank you