List of open source, AI-free alternatives to popular digital services. Decentralization, privacy, activism and ethical business models have also been taken into consideration.

Browsers

LibreWolf: based on Firefox, it has better privacy features and comes with uBlock out of the box. Some streaming services might not word due to DRM licensing, but I haven't had a problem recently with Disney, HBO and Netflix. Finicky to install on MacOS, but they have solutions on their troubleshooting page.
Mullvad: also based on Firefox, has uBlock and their own VPN out of the box. Slightly better privacy than LibreWolf, but that can cause some websites to not work properly (and ultimately why I switched to LibreWolf). Recent controversies might kick it off the list, but for now I'm leaving the decision to the reader's discretion.
Tor (only for specific cases): also based on Firefox, as private as you can get with their onion links, bridges and proxy features. Should not be used as a primary browser and it's not beginner friendly, but it's good for when a certain website is blocked in your country for any reason. I use it when Sci-hub gets locked in Denmark and common free content providers have onion links that are less likely to be down than the regular domains.

E-mail Providers

Disroot: I could talk for ages about Disroot, but they're a free e-mail provider based in Europe that give you access to multiple different services, including cloud storage and online office suite through NextCloud and Cryptpad. I'm a big fan of their core values and privacy policy, and it's supported by volunteers and donations.
Murena: I found out about Murena through their /e/OS, which is a Degoogled Android OS for the Fairphone. They're based in Europe and market themselves as anti Big Tech. I think that it's the best alternative to Gmail and Google Drive in one box, running OnlyOffice* and NextCloud to power their Workspace, however the free plan only comes with 1GB of storage.
Tuta: no free tier as far as I'm aware, but I've seen it recommended in multiple places by people trying to escape Big Tech and Proton (which is pro AI and Israel).

Cloud Storage

NextCloud: Open source and mostly directed at self-hosting. There are public instances, and you can get up to 8GB of free storage through here.
Disroot Cloud powered by NextCloud: Disroot offers Cloud services powered by NextCloud, with 2GB of free storage. It's possible to upgrade the storage, from 11€ per year. Not the largest storage, but convenient if you already have a Disroot e-mail.
CryptPad: CryptPad is an open source, end-to-end encrypted collaborative office suite. They have a few public instances free to use, it's possible to self-host and also subscribe to a paid plan if you need extra storage. Storage upgrade is available through the CryptPad.fr instance and the largest free tier is available through cryptpad.private.coffee with 5GB. They're hosted in France and Austria respectively, and you can check out other public instances hosted in other countries here.

Office Suites

Online

Ellipsus (Writing Only): Fiercely anti-AI, Ellipsus is probably the best option for people looking for a platform to exclusively write books/stories. They're committed to being free forever, but recently released a Plus version, that includes extra features (that are not at all necessary for writing but make the experience richer). Their paid subscription is on a pay-to-own model, meaning that after a certain amount of time the software license is yours and you no longer have to pay, which is in my opinion very ethical.
Murena Workspace: Murena provides an office suite based on OnlyOffice*.
CryptPad: CryptPad not only provides cloud, but also Office Suite apps, based on OnlyOffice*. The end-to-end encryption makes sure your data is always safe and only accessible through your e-mail and password login. It's possible to share the document and collaborate with others, including Suggestions Mode similar to Google Docs, for editing. Storage upgrade is available through the CryptPad.fr instance and the largest free tier is available through cryptpad.private.coffee with 5GB. They're hosted in France and Austria respectively, and you can check out other public instances hosted in other countries here.
Disroot powered by CryptPad: If you have a Disroot e-mail, you can use their CryptPad instance, with 500MB of storage.
dDocs and dSheets: Open source, end-to-end encrypted and free of AI. Minimalist interface that is very familiar for Google Docs users, and supports real-time collaboration and file sharing. You can read their manifesto here. dDocs also supports HTML export for AO3.

Local

LibreOffice: Local and offline, it's very robust and provides all the software you might need from an office suite. It's also open source and very respected in the community. There are also tutorials online showing how to configure the UI to make the experience seem more familiar for people used to Google Docs and Microsoft Office.

*Note on OnlyOffice: despite being open source and used as a base for many platforms, OnlyOffice itself has implemented tools to allow you to connect with an external AI provider. This does not mean the platforms that use OnlyOffice use AI or that you would be using AI automatically by using OnlyOffice directly, but it shows that the company does not have an anti-AI stance. Similarly to LibreOffice, they offer desktop apps you can download and run offline, and also have a cloud based option.

Simple Collaborative Writing

If you only need a quick platform to collaborate with others on a note that will later be moved somewhere else, you can use Disroot through Etherpad. It doesn't require an account, but that also means you might lose your pads if the session cache is cleared.

Disroot through Lufi: anonymous, free, with optional password protection, compressing multiple files into a .zip folder and with expiration date, so your files aren't stored for more than necessary.

Password Manager

Disroot powered by VaultWarden: Open source and one of the favourites for security and privacy. VaultWarden usually requires self-hosting, but Disroot offers a public instance. You don't need a Disroot account to use this service. Built on Bitwarden, I believe you can use Bitwarden services (apps and extensions) with a VaultWarden instance.
BitWarden: open source and cloud based, they also offer mobile apps so you can access your passwords on different devices. They have a free tier that is very generous. Currently looking into their AI policy.

Search Engine

Disclaimer: I'm still doing research on this because none of the options I found so far check all of my boxes: no AI, good privacy policy, no money to Israel, their own crawler for results/not using Google or Bing on the background. A lot of the degoogled alternatives I've seen promoted online usually fail one or two on this list. Here's the options I'm testing right now:

Searchbare: No AI, no search history, no tracking. Uses Brave in the background, which has been involved in some controversies.
SearXNG: Self-hosted or through one of their public instances (including Disroot). It's a metasearch engine, aggregating results from different services. You can see which instances are online and which engines they use here. Redditors report bad results, slow performance and crashing.

Note on popular alternatives: Qwant and Ecosia share data with Microsoft, and Ecosia has recently rolled out AI integration. Startpage is a Google proxy (it protects your privacy but uses their results) and the search engine itself doesn't use AI, but the company has a separate AI app. DuckDuckGo is a Bing proxy (which is owned by Microsoft) and has AI integration (which you can opt-out).

Bearblog: This blog!
Ghost
Magic Pages
PencilBooth

Translation

LibreTranslate
Searchbare Translate

PDF Tools

ILovePDF
DigiPDF

Misc. Digital Tools

La Digitale: Open source and privacy-focused digital tools made for education. Background remover, QR code generation, audio transcriber, short link generator, and a lot more.
DelphiTools: Also available for iOS. No logins, no registration, no data collection.
OmniTools
Searchbare Widgets

Sources

/r/degoogle/
/r/CorpFree/
OpenAlternative: Open source software directory, useful alternative search. However not a guarantee of being free from AI, private or ethical.
awesome-selfhosted on Github: List of open source software available to self-host, most also have an online instance you can use.