Both are mesh networks, with slight differences. The idea is that volunteers run relay nodes with LORA (which has a range od a few KM, depending on visibility), and you also have client devices, and if you have a large local community of enough nodes and users, you can have an off-grid communication network where data is being sent node to node (both client and relay) before it finds the recipient. Both networks are encrypted.
Most cities already have a pretty good coverage. Meshtastic has a few issues that Meshcore tries to solve, mostly in regards to scaling, but tbh I havent researched it enough to be able to correctly list them (just like this answer is mostly a simplification). There's plenty of blog posts that explain it a lot better.
You can get standalone Meshcore devices (with a screen and keyboard) for around 70$, and devices that connct to your phone through bluetooth and you send messages through the network from an app for even cheaper.
My guess is that it's not entirely adversary-proof, but it probably beats having a phone with you to communicate when you're doing anti-goverment sruff.
And if you're asking about Anarchist Library, there's this site that has a lot of articles, zines and books about good operational security, how to behave on protests, what to (not) bring, first aid against common crowd control, and general anti-goverment guirrella stuff so you can protest as safely as possible.
When I was looking through the official marriage papers you submit when oficially requesting marriage, to see what I need to do if we would want to get married, that option simply wasn't there in the checkboxes. And I asked for clarification, and apparently our laws don't allow that combination, at least not as a part of the marriage process.
I haven't really looked into it more, and a friend told me it's very probable that we could just choose one of the available options and then submit a separate request to change my surename to add the missing one. It was also more than a year ago, and someone also told me that our marriage laws did go through a revision recently and it might be actually possible to choose both for both now. I'll have to re-check again, but I'm certain that at least last year, it wasn't possible.
Oh, one option I found a funny loophole was that we could marry, she'd take both, then divorce while keeping our new surenames (so she still has both), then marry again and I'd take both. I would end up with three surenames, mine twice (since she already has both, and I'm keeping mine and taking her current at the point of second marriage), but while that would be pretty funny, realistically it's easier to just file for a surename change after wedding :D
As for the reason, who knows? But an ancient patriarchic custom is probably the reason, I'd guess that especially historically it's not really common for a man to take his wife surename in general, and usually it's just the bride either taking the man's or keeping both.