Thanks trantute2! I wasn't aware of this more modern branch, it seems to have been merged recently to the main Namecoin repo at Github. So those who want to keep in track of the development can also probably use the Github repository:
https://github.com/namecoin/electrum-nmcThe most important change is, obviously, that the critical vulnerability of <3.0.3 should have been solved on Namecoin too.
The branch seems quite new. The commit "Renaming from ..." is only a month old.
I have installed electrum-nmc according to your guide on a Debian system and it installed without problems. As I already had the dependencies of a Bitcoin electrum, I only had to add libusb1.0-0-dev (?) and pyqt5-dev-tools.
Installation procedure seems a bit newbie-unfriendly though, but maybe that's not that bad: According to the beta release notes, Segwit is offered in the GUI but not supported by Namecoin yet so an uninformed downloader could expose his coins to theft (due to the "anyonecanspend" problem).
I do not know, whether the instructions I gave, is the best way to install the program. I started with a new and empty ubuntu installation. Therefore, I specified all dependencies. However, I still was able to mess my system up so that those icon error came up. I had to start from scratch again (new ubuntu installation).
So I think it's pertinent to add the following warning here: If you use electrum-nmc and use it with real Namecoins, don't use the Segwit and P2SH features! It's even better not to use it at all as a real wallet if you don't know exactly what you do ...
Very important and true! If one uses a Trezor, a message pops up, asking for the wallet derivation to be used (see
https://blog.trezor.io/using-trezor-with-electrum-v3-a0b9bcffe26e, the section with mentioning "m/49’/0’/0’"). You MUST use the original way, called Bitcoin/Namecoin
legacy, via selecting
"m/44'/0'/0'" for Bitcoin and
"m/44'/7'/0'" for Namecoin (but correct me if I am wrong).