Hmmm. Is that actually a problem?

I’m just using SMTP server of my email provider, just like in my mail client. Never had any trouble over a couple hundred notifications I send per month. As added benefit, if your mail provider is large, it won’t have problems with sending mail to gmail and such.

SafeInCloud. Not as pure and audited as more known ones, but good enough for me, syncs over webDAV and has native clients with actually good UX.

I also run a backup instance of Vaultwarden in case I need some passwords on a new device over LAN/VPN.

Not exactly fitting, probably, but self-hosted sync for Chromium browsers. Not xbrowsersync, but full-fledged, like Mozilla’s, with syncing extension settings, sending tabs, etc.