Does restarting your router help in these moments? Might just be an underpowered router
Do your devices use the router's DNS? If so is it still reachable? From the client? From the router machine?
Might be some kind of DHCP bug too but I'm not well versed in it
I don't think they require Nextcloud. Consider LaSuite Docs too if you need something simpler
FWIW, you can use Headscale's embedded DERP server, or host your own. They need a STUN port and an HTTPS port
Ntfy can send/receive notifications to/from the phone. You can selfhost it or use a public instance. For the healthcheck app, consider Uptime Kuma as it has ntfy integration. But a simple cron script that monitors + cURLing ntfy when it fails could also be used.
Protocol-wise, OIDC is generally the most supported out there. LDAP too, to an extent.
Software wise, I find Kanidm quite simple to set up (basically just one container). It's mostly managed via the terminal though, and lacks some eyecandy. But some of the examples in its docs should be easy to follow and get you familiar with mapping scopes/groups between Kanidm and services.
Authelia is okay too
I believe as of now, the databases do not diverge and hence a binary swap/container image swap is doable. If you already set up SSO logins, then I'm not sure because Continuwuity doesn't support that yet.
Please re-ask the question with the folks in #continuwuity:continuwuity.org to be extra sure before doing anything. Oh and without saying, do clone and backup the data paths for easy reverts later
It's claimed to be official. But I went with https://continuwuity.org/ since it seemed to have a more active community. Plus ever since then, the core maintainer of Tuwunel has been making threats against Continuwuity including personal attacks, and seems to be quite unpleasant to deal with in general. There's also been a thread about it here. So I honestly lost all taste to reconsider.
For Matrix consider Continuwuity instead of Synapse if you want something easier to maintain. You'll also want to set up Element Call (i.e. the "new" calling stack) for wider client support.
Notifications can be unreliable but it depends on your push provider (e.g. don't use the default ntfy.sh instance, use another one or selfhost yours). Do let me know of any other nits though.
For XMPP, notifications is most reliable as it maintains an in-band connection to the server. A/V is a bit more lacking, as mobile clients can only do 1:1 calls, and it misses some smaller features compared to matrix. But it's very lightweight and should be more than capable for use with family and friends.
Try
nslookup testdomain.comfrom your laptop (this uses your router DNS by default)Then try
nslookup testdomain.com <your-router-ip>from your laptop (this forces using your router DNS)Then try
nslookup testdomain.com 1.1.1.1from your laptopThen repeat all 3, but on your router. Just to see where the problem is exactly