Agreed, though I don’t think they disabled systemd-resolved, because it still works using 127.0.0.53 when they’re connected to the VPN. So the daemon must be running, unless Mullvad itself has a DNS forwarder using the same loopback. I suspect they either hard coded some upstream DNS server for Mullvad, because Mullvad might not have supported systemd-resolved yet. Or maybe they set a permission on the configs, and something changed with the user context of Mullvad processes.

Interesting that it works when the VPN is connected, though. I also believe that systemd-resolved is installed on just about any system using systemd, but often isn’t enabled, without problem. Enabling it would generally involve a resolv.conf symlink and a config, so maybe that config was hijacked by Mullvad (or OP configuring Mullvad), and there’s no upstream DNS server available when the VPN isn’t connected.

I missed that it’s Linux Mint in the original post, and it looks like Mint has started using systemd-resolved. The Arch wiki might be useful to OP on how things are configured:

https://wiki.archlinux.org/title/Systemd-resolved

Ok, so something setup 127.0.0.53 as your DNS server, and isn’t removing it correctly. I think it’s safe to say it’s Mullvad, since it works using that DNS server IP when connected. Is that IP in your resolv.conf, or is resolv.conf maybe a stub, and you’re using systemd-resolved?

Ok, so does the VPN bring it’s own DNS? Some VPNs do, so it may explain why everything suddenly works fine when you connect.

When not connected to VPN, are you able to dig or nslookup internet names? Local names? A server timeout will be very different from an nxdomain or an empty SOA, in the response.

Are you able to telnet to a public web server on TCP/443?

One thought I’m having is, maybe at some point you set a static IP on your wifi interface, but screwed up the subnetting.

Have you ever messed with network manager or systemd-resolved internal settings, maybe trying to setup multicast DNS or caching?

I’d say if you get a Ryzen, yeah. I have a P14s gen4 AMD that I use for my primary machine, and game on successfully. But I also have an old T14s gen1 AMD that work let me keep when I got refreshed. Right now I have Windows on it, to play some games that don’t work well in Proton, but it works fine in Linux as well.

If you can swing it, the T14s gen3 with a Ryzen 7 6850u was a truly excellent machine, it’s what I have for work right now. But we won’t see it coming off lease for another couple years, so it’s a bit early for good prices on the used market.

Just grab a 3-4 year old 13" business class laptop, like a Thinkpad X13. When they come off lease at 3-4 years, they hit the used market at pretty great prices. Some are in rough shape, but use trusted sellers who sell at reasonable volume, and their condition grading tends to be pretty reliable.

Be careful about upgradable RAM, or getting at least 16GB. It sounds like you’d be fine with 8GB for now, but 16GB will get you better life out of the machine.

You may want to replace the SSD straight away, depending on the write cycles. I’d probably just grab one with 256GB, and get a replacement straight away. Lenovo has all their hardware maintenance manuals online, to make checking compatibility and performing the upgrade pretty easy.