To playback DRM content, such as Netflix, and here in the Netherlands npostart.nl , you need Widevine. Normally this is provided by Google / Chrome, except that they don't support open source like Raspbian. Strange, because Google Android draws heavily on open source linux.
Very childish of Google. Didn't we have something similar with playback of DVD on linux, some 20 years ago, where we needed a hacker plugin for descramble, that was so simple that the source code fits on a t-shirt?
Do not install the special Chromium with built in Widevine!
The fix is to install an unofficial version of Widevine, published around March 2021 by the same developer of the special Chromium version that includes Widevine. This is a great fix, because the special Chromium version means that you would be stuck with an outdated 2017 browser, Chromium version 58. Not only do you not benefit from security improvements of versions 59 to 92 (as of aug 2022), but also will you have trouble upgrading your system as several packages depend on a newer version of Chromium. The Widevine package works with the normal Chromium browser from the Raspbian distro. But with firefox-esr I don't have success yet :-(
sudo apt-get install libwidevinecdm0
It is a little bit special that the official Widevine requires a 64-bit OS, while this unofficial version only functions on 32-bit. In case you run a RPi4 with 8GB and Pi OS(64-bit), you can install the same widevine package, but have to figure out how to run a 32-bit version of your browser.
This unofficial widevine package should be the perfect solution for OP, because (s)he is running a 32-bit OS.