I use a ProtonMail address for online accounts whose content I don't need intermingled with my personal mail. I also use a ProtonMail "+" alias when signing up

I use a ProtonMail address for online accounts whose content I don't need intermingled with my personal mail. I also use a ProtonMail "+" alias when signing up for a totally new service (with a filter to place emails from that alias directly in Spam; as all it does is handle account signup/verify). If I can't change my email after signing up for a service I don't continue using that service, as I define that to be user-hostile. If I can't use "+" in an address when signing up I default to GetNada. The other use case for a PM address is for anonymity (e.g. throwaway/whistleblowing) with a requisite VPN and browser-only login, etc. As an aside, I use a free Outlook address as my newsletter spam box (good storage size and Android interoperability for consuming content).