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Microsoft pulls MS365 Business Premium from nonprofits
(www.theregister.com)
This is a most excellent place for technology news and articles.
LibreOffice
And perfectly working software that covers whatever else MS365 offers, e.g. Thunderbird
I'd love for more people to change to Linux, but these are all (also) Windows software.
And if you need it in a browser, there is Collabora, which exists as a paid business version with support or a free non-support version, that can easily be deployed with Nextcloud. Another alternative would be CryptPad.
If you also need your mails in your browser, there are multiple providers like mailbox.org that offer mail encryption even through the online mail interface.