@Phaserune all my sim cards are on the O2 network, no Telekom sorry. I've not heard form anyone having problems with Telekom network though. If you're running stock PureOS please file an issue at https://source.puri.sm/Librem5/OS-issues/-/issues reporting if e.g. data and SMS are working (if so it's likely not carrier related).
@agx Do you have any tips for me getting the Librem 5 phone calls working on Deutsche Telekom? I ask because you are German and I know you are using your L5 a lot. Danke auf jedenfall!!