Good softphone software for VoIP telephony?

I'm looking for good software to make phone calls from a PC or notebook. I have already looked at some applications, but would still like to hear which one you can recommend to me. If possible, the software should be offered for all platforms.

I use the free version of Zoiper on Linux and Android. Works very well for me.

However, Huawei is somewhat hardcore with energy saving and thus prevents Zoiper from receiving calls when it is in standby. This may affect all softphone solutions.

Thanks for your answer. Smartphone doesn't matter to me, the router manufacturer's software is enough for me. Since I'm already working from the computer, I also want to make my phone calls about it.