The language is vague because it's a generic policy to follow, not "Portugal will replace all MS Office with LibreOffice". That's how policies work, they're generic guidelines to follow.
Suspect projects include GAIA X (https://en.wikipedia.org/wiki/GAIA-X#Controversies). It will probably have the same success as the NHS software fiasco, which wasted £10bn:
https://www.theguardian.com/society/2013/sep/18/nhs-records-...
And again, various EU countries open source software they've created, or data they have for that matter ( open data). Your contemptuous pessimism is fully unwarranted.
The real question is: What sort of circumstances drive a government to develop something "in house" that they'll later open source, or adopt an open source solution, when that competes with giving the government contract to your industry cronies.
It would be real nice, if we could get a clear policy framework that basically just says: Whenever open source is an option, the government must go with open source. But we are far away from anyone in power clearly calling for that.
And we've seen some real setbacks where that is concerned: For example the city administration of the city of Munich had that policy in the late 00s / early 10s, to the point where they had migrated 15000 workstations to Linux in 2013, shaving €10M/yr off the Microsoft tax.
All it took was some government officials getting frustrated over a glitch in the e-mail server once in 2017 and compatibility issues about MS Office vs OpenOffice and they reversed course and decided to migrate everything back to Windows by the end of 2020. (It definitely had nothing to do with Microsoft moving their German headquarters to Munich in 2016, if you're naive enough to believe that). -- Don't know the extent to which that actually happened.
As I'm researching this right now on Wikipedia [2], I'm seeing that apparently the new government decided to reverse course back to open source in 2020. -- Don't know the extent to which they've actually finished/begun anything here.
I've also dug into European funding schemes that maintainers of open source projects can tap into for their own living expenses in recognition of their contribution to open source. -- That is incredibly thin. You'd have to be a maintainer of a superstar open source project if you want even the minutest chance at a one-off stipend of up to €50k.
Compare that to how science funding works: I travel extensively in circles of people who do EU-funded science projects and many of them will readily admit that they are downright embarrassed by how little value they create in return for that funding that they get from the EU. These science projects quickly run into the millions, even when they are quite small projects, and the total budget at the government level is quite considerable. When compared to that, the money that they sometimes throw at open source seems like a symbolic amount at best.