I’m a EU citizen and I’ve always been intrigued by Estonia’s digital citizenship. I’ve only picked a few tidbits about how it works and they may be wrong, so take this with a grain of salt.
From what I understand, a digital citizenship is different from a normal citizenship. It allows you to, for example, open a company, but I don’t know if it gives you enough to make you a EU citizen. In Portugal there’s a bit of a kerfuffle about the Golden Visa programme[1] because it’s seen as a way to buy EU citizenship for cheap[2] and cause problems for nationals[3]. I’m not aware of the same happening through Estonia, so it makes it me think it doesn’t give you EU citizenship.
In addition, you have to actually go to Estonia to set up the digital citizenship; it’s not something you can do completely offline and be done with it.
Methods such as marriage are not that effective in Portugal, at least at the moment. I know of two people with legitimate reasons to get Portuguese citizenship and the process has been a chore, taking years.
[1]: https://en.wikipedia.org/wiki/Portugal_Golden_Visa
[2]: Yes, you need to invest, but you keep your investment.
[3]: House prices in major cities and surrounding areas are through the roof.