The most complete launcher with a ton of extensions probably is Ulauncher on desktop linux. I prefer to use Albert launcher for the time being, because the filesearch plugin uses its own index. On Ulauncher it's too slow. It might change with the upcoming ulauncher v6 (in beta right now).
In any case Ulauncher has many many extensions. It doesn't have a reddit extension but it has a "save to notion" and AI extensions in stable V5 branch right now.
Maybe most people using Mailbox know about this but I'll still mention that using Mailbox kinda requires having your own domain.
Reason is the same as Posteo (unless Posteo changed something lately) : mail adresses will get recycled after some time when you stop using the service and close your account.
Most other providers blacklist adresses so they can't get reused when an account gets deleted.