Well, thanks a lot joniboini, that did it! I'd never had such an appimage before. It took a while for it to react, so after 30 secs of repeated clicking I ended up with about 10 or 15 Electrums wanting to open all at once 
, but otherwise everything's fine. The GUI, fonts etc. are much smaller than they used to, but it's all still quite readable.
Just a detail: is there a way to replace the default (I assume) appimage icon with Electrum's own icon, i.e. the icon of that Desktop Configuration File?
For future reference: I'm puzzled by your explanation about the 404 error to me a 404 is, has always been, something missing on the server, and I can't see how my network should affect that, nor how changing my DNS (easy enough with the VPN) should make a difference. Unless you mean that my DNS could be rejected by the download server? That would be a first, even if it does happen occasionally that a server takes exception to one among the wide varying array of my VPN's servers. Also: if, more likely as I understand things, it's due to the Ubuntu update server, how/where do I change this? Like, it's the Terminal that's deciding for me, isn't it? Btw., that IP 91.189.88.152 says nothing to me.
, but otherwise everything's fine. The GUI, fonts etc. are much smaller than they used to, but it's all still quite readable.Just a detail: is there a way to replace the default (I assume) appimage icon with Electrum's own icon, i.e. the icon of that Desktop Configuration File?
For future reference: I'm puzzled by your explanation about the 404 error to me a 404 is, has always been, something missing on the server, and I can't see how my network should affect that, nor how changing my DNS (easy enough with the VPN) should make a difference. Unless you mean that my DNS could be rejected by the download server? That would be a first, even if it does happen occasionally that a server takes exception to one among the wide varying array of my VPN's servers. Also: if, more likely as I understand things, it's due to the Ubuntu update server, how/where do I change this? Like, it's the Terminal that's deciding for me, isn't it? Btw., that IP 91.189.88.152 says nothing to me.