It depends on what you're looking for.

File storage - plenty of solutions, though make sure you don't pick one that rents their storage space from AWS or Azure.
Personally I use Tresorit at it is end-to-end encrypted, easy to use and has a native client for almost every system I use (except for FreeBSD) in addition to the web interface. On your PC you get a network drive but can also include folders located elsewhere. It's by no means the cheapest solutio though.

For pictures there's Ente. It works very well, is cross-platform, and you can even set up your own server if you're so inclined.

Sadly there's no real alternative to Microsoft's 365 offers - maybe a combination of lifetime MS Office licences or LibreOffice plus some cloud storage provider comes close.

To replace Teams you could use a secure messenger such as Threema Work (this version comes with user management and a versatile inbuilt MDM) and your own Jitsi videochat server. We've replaced Teams with this combo years ago and never looked back.

Hosted Exchange can be rented from many service providers, running on either genuine MS Exchange or a compatible third-party system such as KerioConnect.

There are also other places such as Proton that offer several services at once.

Or are you looking for something completely different?