Question about ASUS WL-Router RT-BE88U

I'm about to get fibre optics. My problem is that Salt, Swisscom and Sunrise don't offer a bridge mode on their fibre boxes for private customers. How can I avoid double NAT under these conditions? I understand that I'm losing interest in my ASUS router (QoS, NAT gaming, etc.) if the two devices are both doing routing. Is there a clean solution (DMZ, IP passthrough, other) that you recommend? PS: I'm doing my tests on https://www.waveform.com/tools/bufferbloat.