They should pass a resolution that all EU member nations shall create official Mastodon and Lemmy instances. Moderators and admins would be actual jobs constrained by the relevant national or EU law.
(Or replace Mastodon and Lemmy with whatever open platforms you deem appropriate)
The browser-based versions of the M365 apps work great* for me in Firefox tabs on Linux. I prefer them being just apps/sites that I use as needed and not deeply integrated with the OS just because the same company made the two.