Aw half the fun of linux is all the weird janky software some nerds felt strongly enough about to release.
Npp can be replaced by several different linux tools. You just have to like using the terminal a bit. Personally I get it. I know awk and sed and all those crunchy tools the olds made exist, but it’s not a crime to have it all in one place in a gui. That said it npp 1000% works under wine. Sublime Text has a linux version and all the plugins you could ever want if you’re willing to learn new ways of doing stuff you’ve already figured out. Vscodium is also a decent npp replacement. It’s fast, has a cli, and a great plugin ecosystem.
Excel is all hype. Unless you’re a data analyst or numbers nerd LibreOffice Calc has all the things. It’s not as performant as excel with large datasets, but it has formulas, pivot tables (though somewhat weird), and macros. It’s just ugly installed from the debian repo. Also if you’re paying for office you can probably still use excel in the browser.
OneDrive sucks, unless you are committed to the Microsoft ecosystem. If you find a suitable replacement for excel, you could always cancel your office subscription and setup a nextcloud instance. You can have it all hosted for you through nextcloud and they have web based office tools using LibreOffice. Their syncing app works on everything so you’ve got options. Or you can try to self-host it. I have a raspberry pi with an external hard drive attached running nextcloud, and a vpn. Reasonably stable, if slow.
I hope that outside of Visual Studio, you can completely free yourself of the windows ecosystem.
I set my mom (62) up an old laptop running Ubuntu last year when her laptop was stolen out of my sister’s car. She’s adjusted fairly well to it. She needed a lot of hands on support at first and any time she uses her printer, but she has figured out how to do a lot of things on it on her own.
She makes papercraft activities in inkscape for a weekly storytime she hosts at a bookstore and has gotten very proficient, but still needs some hand holding when printing errors crop up.