I think you have it backward. Notifications come from your email client after it polls the email server. So you need an email client on your android device that checks the server.
No need to self-host anything, unless you want to self-host your own email server, something that (while doable) is NOT to be taken lightly and will undounbtely lead to difficulties and lots of hiccups down the road.
I am currently self-hosting my email server (bee, doing for almost 20y) but not at home and absolutely can confirm it’s very complex to setup properly.
No, the router being the SPOF (single point of failure) is totally avoidable.
At mny home (no SaaS services offered, but critical “enough” for my life services) i have two different ISPs on two different tecnologies: one is FTTC via copper cable (aka good old ADSL successor) plus a WFA 5G (much faster but with data cap). Those two are connected to one opnSense router (which, indeed, is a SPOF at this time). But you can remove also this SPOF by adding a second opnSense and tie the two in failover.
So the setup would be:
Then in both opnSense i would setup failover multi-WAN and bridge them together so that one diyng will trigger the second one.
edit: fixed small errors
I will finish writing that on my wiki today at https://wiki.gardiol.org/doku.php?id=services%3Alemmy
edit: page done!
Actually much easier than I thought.
Went the docker way and only did a few errors… Took two tries to get everything in order. I am documenting the process here https://wiki.gardiol.org/doku.php?id=services%3Alemmy but the page is far from complete…
edit: i just finished updating the page, it should contain more or less all the issues and solutions i encountered.
Its nice and pretty nerdy. As web based nmarkdown editor in pretty good and the extra features rocks.
It has a few quirks I don’t like though, on the self-hosted side:
But from functionality point of view, I love it