This has been happening on my OnePlus 7 Pro since the release of OxygenOS 10. The userspace backend works fine. Not sure if the issue is exclusive to OxygenOS 10 or Android 10.
You can read more here and in other custom kernel threads:
https://forum.xda-developers.com/search/thread/3936434?query=wireguard
XDA user B1oH4zard identified a possible cause in the kernel module thread
https://forum.xda-developers.com/showpost.php?p=81125845&postcount=275
WireGuard Kernel/ROM Integration - Post #0
few months ago i build wireguard module for xiaomi mi9 and have same problem, need remove rmnet_iperf module before loading wireguard, it us...
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