This tool is expected to be used to attach any number of Hyper-V virtual switches to a WSL2 virtual machine (eth1, eth2, eth3, ...).
Get prebuilt binaries from Releases or Actions artifacts 
.
If your need is not to attach multiple switches, but to replace the switch to which the default (eth0) NIC is attached,
then it is officially available on WSL2 preview, check this comment for details.
--network <network> Network name or GUID. Example: Ethernet
--mac-address <mac-address> Optional. Fix physical address of network interface to this mac address if specificated. Example: 00-11-45-14-19-19
--version Show version information
-?, -h, --help Show help and usage information
root@WSL ~ # # Check existing interface
root@WSL ~ # ip link
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
......
6: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000
link/ether 00:15:5d:f3:58:46 brd ff:ff:ff:ff:ff:ff
root@WSL ~ # # Attach to Hyper-V virtual switch "New Virtual Switch"
root@WSL ~ # /mnt/c/some/random/path/WSLAttachSwitch.exe --network "New Virtual Switch"
root@WSL ~ # # Now we have a new interface "eth1"
root@WSL ~ # ip link
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
......
6: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000
link/ether 00:15:5d:f3:58:46 brd ff:ff:ff:ff:ff:ff
7: eth1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
link/ether 00:15:5d:e0:01:0c brd ff:ff:ff:ff:ff:ff
root@WSL ~ # # Make use of new interface
root@WSL ~ # dhclient eth1WSLAttachSwitch.exe --network Ethernet
WSLAttachSwitch.exe --network Ethernet --mac-address 00-11-45-14-19-19
WSLAttachSwitch.exe --network Ethernet --mac-address 00-11-45-14-19-19 --vlan-isolation-id 2
This tool needs to be run again if the WSL VM has been restarted.