Based on the grugq's famous gist, the tl;dr on what to worry about
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Use a Google Pixel or an iPhone, nothing else.
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Use encrypted messengers, Signal, WhatsApp, iMessage. Don't use SMS
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Use Windows 10, patch it. If you're wondering what to buy, any with the Secured Core brand, or anything by Microsoft.
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2FA all your logins, use a password manager (doesn't matter which one)
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Use Chrome or Edge, nothing else. Or Vivaldi.
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Don't trust email providers. If you do, trust Microsoft and Google.