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MeWe - Recommended Facebook replacement.

MeWe is probably the closest like for like replacement for Facebook, with similar features (minus the ads and spyware).

Also consider

If you are technically minded you could consider building and/or hosting a site for you and your friends. Projects like Friendica and Hubzilla could help with this.

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Gridsome - Recommended Gatsby replacement.

Like Gatsby, Gridsome collects data from various sources and generates a static site from it. Gridsome is a Vue alternative to the React based Gatsby.

Also consider

For static site generators more broadly, also take a look at Eleventy and Hugo.

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Vue - Recommended React replacement.

Vue is a JavaScript framework for building user interfaces, and has much in common with React. There are many such frameworks, but React and Vue are currently the most popular.

Also consider

If you are willing to try something less established, Svelte and Alpine.js both make for interesting alternatives.

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Telegram - Recommended WhatsApp replacement.

Telegram is a messaging app, available for all popular platforms. It looks and feels a lot like WhatsApp, and can serve as a direct replacement for it.

Also consider

If WhatsApp wasn't a perfect fit in the first place, apps like Signal or Discord might better suit your needs.