I’ll answer your question more generically, in the form of an explanation, and as an update on the current goings on:
The Belgian COVID checker app, like the Finnish app, the French app and all the others in the EU zone, are all more or less direct derivatives of the DGCA Verifier App, which is the EU’s reference implementation. In other words, when a feature makes it into the DGCA Verifier app, eventually (days to weeks later) it may or may not trickle down to your local version, depending on what your local authorities reckon is useful to keep or not to keep from the reference application.
In the case of the NFC feature, it’s always been in the DGCA Verifier app. From what I can tell from the git log, it used to work, then the author / maintainer of the NFC feature fucked it up on purpose for some reason, and I made a pull request to essentially unfuck it a couple weeks ago. If the NFC feature was ever enabled in one of the national implementations, no doubt it was disabled in a hurry when the feature got fucked up.
But most likely it was never enabled in any national implementation, because it turned out QR codes sort of naturally won out and left the NFC option behind altogether.
So my advice to you is this: if you want the Belgian CovidSafe app to support NFC, get in touch with the local maintainers of that app and urge them to enable the NFC feature in the DGCA Verifier app in their own implementation (and since you’re at it, tell them to urge the DGCA Verifier app maintainers to accept my fucking fix, because the EU being the EU, they still haven’t even reviewed it, despite being a TWO LINE FIX!! )
You might have to argue the case in favor of NFC - because you know, they’re public servants and they don’t like to work if they don’t have to. If you need arguments, I can send you the powerpoint I sent the Finnish authorities for that very purpose, and you can use the video above to shows a real-life example of NFC COVID certificate checking in action.
As for the update: the Finnish authorities told me they’d review our request in January, because they have “other important things to do at the moment” and now is not a good time. Whatever… So anyway, if NFC happens in the Finnish app, it won’t happen before January at best. Probably February. Who knows… COVID might be gone by the time NFC gets enabled