Master has support for kernel v5.10 on x86_64, if you select KERNEL_TESTING. That does require building from source, but due to this being x86_64, there is no risk of bricking.
It would be conceivable to backport rtl8125b support to the openwrt-21.02 branch with kernel 5.4, but someone would have to isolate the necessary patches adding this to r8169 and doing the actual backporting and testing. Not a trivial effort, but reasonable for someone with medium experience and motivation, but I wouldn't expect that more experienced developers or regular contributors will volunteer for this job (master and kernel 5.10 are just closer at hand - and the targets (x86_64/ RPi4+) generally easy to update).