NL and BE have gotten rid of most of the restrictions now. Germany is slowly phasing them out, but masks are still required inside.

The differences between countries so close together are silly. Last night, I was at a concert in Belgium. No rules at all. It was a full house (not sure how big but definitely several hundred people), no certificate of any kind needed, no masks.

Today I went to a gig in Germany. Small gig at a tiny cafe,
probably only around 20-30 people there. Show proof of vaccination and wear a mask unless you're seated.
And they almost didn't want to let me in because I haven't gotten my booster yet which is NOT a requirement in Germany. 2 shots still qualifies as fully vaccinated and let's you into places which have either 2G or 3G. But the venue was re-opening tonight and no-one knew about the rules for "only" 2 shots. In the end they told me it's me who's taking the risk and let me go inside.