My stuff in the cloud
The majority of my "stuff" lives on various cloud services, so what is actually on my desktop or "backed up" is never really an issue.
What I'm listing below is my personal setup, meaning that these aren't really the collaborative tools I use for people and projects, beyond "Boris Rachael Shared" folders on various things.
Github
I have a personal paid plan. My local Developer folder has checkouts of all sorts of things, but I don't tend to have stuff that isn't pushed upstream regularly.
OneDrive
Paid 1TB of storage that I'm on an annual family plan with my parents. My mom uses the traditional (Mac) Microsoft apps on desktop, and this came bundled with it.
I now also have her setup so that her working files all live in OneDrive and we don't have to worry about backups for her machine either.
I don't have the app installed, this is long term archive stuff. 200GB of stuff that I should look at, at some point?
iCloud
I have a Family plan with Rachael of 200GB. I keep all my working files – Downloads folders, Desktop/Screenshots, Documents – in iCloud.
I say working files, but I don't work with a lot of desktop files other than Keynote presentations.
iTunes Match
My music is all up in iTunes Match and/or I can re-download Bandcamp purchases. Recently, my Ampache TinyHome Install means that I may be cancelling this before it renews at the end of 2025.
Photos
Over 100GB of photos on my phone, this is also all in iCloud. This ends up syncing to my Photos app on desktop.
I have an Amazon Prime account that bundles unlimited photo storage in Amazon Photos. I haven't kept it synced and up to date.
I have a historical archive of Flickr backed up, but also imported it all into Amazon Photos.
Nextcloud
I have a Nextcloud install on Commons Computer that replaced my (free, historical) Dropbox usage with its built in "Files" app. This has a WebDAV interface so accessible from Mac desktop.
Not super active, but I'm considering how I can use it more.
Google Account
I have a paid personal GSuite account that runs email and calendaring.
I end up using GDrive a fair bit for ad hoc sharing and projects of all kinds. Make a folder, share it with a handful of people, have a GDoc for some updates.
Some GSheets I can replace with Grist for more Airtable-like use cases, but finance, budgets, and just general quick shared sheets are easiest with GSheet.
I'll mention Commons Computer and TinyHome as my two main Cloudron installs where I run a bunch of self-hosted things.