As you can connect to the internet you can also access your router (or at least a router). And when running ping, even if you had overlapping IP addresses you should still get responses from the network.

So, two things come to mind: Either your laptop is running with a different netmask than other devices which causes problems or you’re connected to something else than the local network you think you are. Changes on DHCP server or misconfigured network settings on the laptop might cause the first issue. The second might be because you’re connected to your phone AP, some guest network on your devices or neighbors wifi by accident (multiple networks with same SSID around or something like that).

Other might be problems with mesh-networking (problem with ARP tables or something) which could cause issues like that. That scenario should get fixed by reconnecting to the network, but I’ve seen bugs in firmware which causes errors like this. Have you tried to restart the mesh-devices?

Is it possible that your laptop has enabled very restrictive firewall rules for whatever reason? Check that.

And then there’s of course the long route. Start by verifying that you actually have IP address you assume you have (address itself, subnet, gateway address). Then verify that you can connect to your router (open management portal, ping, ssh, all the things). Assuming you can, then check the router interface and verify that your laptop is shown there as a dhcp-client/connected device (or whatever term that software uses). Then start to ping other devices on your network and also ping your laptop from those devices and also verify that they have addresses you assume (netmask/gateway included).

And so on, one piece at the time. Check only single thing at one time, so you get full picture on what’s working and what’s not. And from there you can eventually isolate the problem and fix it.

It’ll always ask for the default configuration after hard reset. So, no, you won’t lose it forever.

That’s better, but you still need to have single wire to loop it around, which is not normally accessible. And at least in here the term ‘multimeter’ spesifically means one without a clamp, so you’d need to wire the multimeter in series with the load and that can be very dangerous if you don’t know what you’re doing.

Also, cheap ones often are not properly insulated nor rated for wall power (regardless of your voltage), so, again, if you don’t know what you are doing DO NOT measure current from a wall outlet with a multimeter.

or multimeter

Unless you really know what you’re doing DO NOT measure current on a wall outlet with a multimeter. Specially not with a cheap one. That can pretty easily break your hardware, burn your house down and kill you, not necessarily in that order.

“Enough battery life” is a bit wide requirement. What you’re running from that?

Most of the ‘big brands’ (eaton, apc…) work just fine with linux/open source, but specially low end consumer models even from big players might not and not all of them have any kind of port for data transfer at all.

Personally I’d say that if you’re looking for something smaller than 1000VA just get a brand new one. Bigger than those might be worth to buy used and just replace batteries, but that varies a lot. I’ve got few dirt cheap units around which apprently fried their charging circuit when the original battery died, so they’re e-waste now and on the other hand I have 1500VA cheap(ish) FSP which is running on 3rd or 4th set of batteries, so there’s not a definitive answer on what to get.