Hi, with linux-image-5.4.0-4-amd64 version 5.4.19-1 from Debian/testing AMD64 I can confirm this.
I did this to fix it: root# cd /lib/firmware/rtl_nic root# wget https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/plain/rtl_nic/rtl8125a-3.fw NOTE: Might need to do `update-initramfs` for people having the hardware. For details see commit "rtl_nic: add firmware rtl8125a-3" [1] saying: This adds firmware rtl8125a-3 for Realtek's 2.5Gbps chip RTL8125. Thanks. Regards, - Sedat - [1] https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/commit/rtl_nic?id=f667c005600bd4fe24a0a439b7a3f3eadcce753a