Nextcloud. Do not forget to backup your data and sql db. Use mariadb or postgresql on initial setup and configure php-fpm, opcache and other tunings you may refer to documentation
Actually they all the same. Best thing you could do is self hosting like nextcloud and talk or matrix, use searx, pihole dns etc... to have your data on your server other than that all companies are the same in terms of privacy
I use FOSS applications as much as I can and try to avoid all samsung and google apps. In addition to that I'm always on pi-hole network to block background network requests by Samsung/Google
I still have this on my steam deck via dreamcast emulator.