With config_dummy enabled for KVM kernels (bug 1998244) this test is now failing with:

 Running 'make run_tests -C net TEST_PROGS=rtnetlink.sh TEST_GEN_PROGS='' TEST_CUSTOM_PROGS='''
 make: Entering directory '/home/ubuntu/autotest/client/tmp/ubuntu_kernel_selftests/src/linux/tools/testing/selftests/net'
 make --no-builtin-rules ARCH=x86 -C ../../../.. headers_install
 make[1]: Entering directory '/home/ubuntu/autotest/client/tmp/ubuntu_kernel_selftests/src/linux'
   INSTALL ./usr/include
 make[1]: Leaving directory '/home/ubuntu/autotest/client/tmp/ubuntu_kernel_selftests/src/linux'
 TAP version 13
 1..1
 # selftests: net: rtnetlink.sh
 # PASS: policy routing
 # sysctl: cannot stat /proc/sys/net/ipv4/fib_multipath_hash_policy: No such file or directory
 # Error: Multipath support not enabled in kernel.
 # sysctl: cannot stat /proc/sys/net/ipv4/fib_multipath_hash_policy: No such file or directory
 # sysctl: cannot stat /proc/sys/net/ipv4/fib_multipath_hash_policy: No such file or directory
 # sysctl: cannot stat /proc/sys/net/ipv4/fib_multipath_hash_policy: No such file or directory
 # RTNETLINK answers: No such process
 # FAIL: route get
 # PASS: preferred_lft addresses have expired
 # PASS: promote_secondaries complete
 # RTNETLINK answers: Operation not supported
 # RTNETLINK answers: Operation not supported
 # RTNETLINK answers: Operation not supported
 # We have an error talking to the kernel
 # RTNETLINK answers: Operation not supported
 # We have an error talking to the kernel
 # RTNETLINK answers: Operation not supported
 # We have an error talking to the kernel
 # RTNETLINK answers: Operation not supported
 # We have an error talking to the kernel
 # RTNETLINK answers: Operation not supported
 # We have an error talking to the kernel
 # RTNETLINK answers: Operation not supported
 # Dump terminated
 # RTNETLINK answers: Operation not supported
 # We have an error talking to the kernel
 # RTNETLINK answers: Operation not supported
 # Dump terminated
 # RTNETLINK answers: Operation not supported
 # FAIL: tc htb hierarchy
 # add tunnel "gre0" failed: No such device
 # Cannot find device "neta"
 # Cannot find device "neta"
 # Cannot find device "neta"
 # Device "neta" does not exist.
 # Device "neta" does not exist.
 # Device "neta" does not exist.
 # FAIL: ip netconf show neta
 # Cannot find device "neta"
 # FAIL: gre tunnel endpoint
 # Error: Unknown device type.
 # Cannot find device "gretap00"
 # Cannot find device "gretap00"
 # Cannot find device "gretap00"
 # Error: Unknown device type.
 # Cannot find device "gretap00"
 # FAIL: gretap
 # Error: Unknown device type.
 # Cannot find device "ip6gretap00"
 # Cannot find device "ip6gretap00"
 # Cannot find device "ip6gretap00"
 # Error: Unknown device type.
 # Cannot find device "ip6gretap00"
 # FAIL: ip6gretap
 # Error: Unknown device type.
 # Cannot find device "erspan00"
 # Cannot find device "erspan00"
 # Cannot find device "erspan00"
 # Error: Unknown device type.
 # Cannot find device "erspan00"
 # Cannot find device "erspan00"
 # Cannot find device "erspan00"
 # Error: Unknown device type.
 # Cannot find device "erspan00"
 # FAIL: erspan
 # Error: Unknown device type.
 # Cannot find device "ip6erspan00"
 # Cannot find device "ip6erspan00"
 # Cannot find device "ip6erspan00"
 # Error: Unknown device type.
 # Cannot find device "ip6erspan00"
 # Cannot find device "ip6erspan00"
 # Cannot find device "ip6erspan00"
 # Error: Unknown device type.
 # Cannot find device "ip6erspan00"
 # FAIL: ip6erspan
 # PASS: bridge setup
 # PASS: ipv6 addrlabel
 # PASS: set ifalias 8e7ce1cf-21e0-44e2-93b2-e66bae59e79b for test-dummy0
 # Error: Unknown device type.
 # FAIL: can't add vrf interface, skipping test
 # PASS: vxlan
 # SKIP: module fou is not found
 # Error: Unknown device type.
 # FAIL: can't add macsec interface, skipping test
 # PASS: ipsec
 # SKIP: ipsec_offload can't load netdevsim
 # PASS: bridge fdb get
 # PASS: neigh get
 # SKIP: bridge_parent_id can't load netdevsim
 not ok 1 selftests: net: rtnetlink.sh # exit=1

This would require at least:
CONFIG_VRF
CONFIG_MACSEC