reproducer on bare metal machines:

#!/bin/bash
#                 br0
# Host A       -- SA ---   Host B
# 192.168.0.1             192.168.0.2
# 2000::1                 2000::2
#   |                       |
# wg: 10.0.1.10          wg: 10.0.1.11
#     fec0:1::a              fec0:1::b

IN_V=6
MASK[6]="64"
HA_IP[6]="2000::1"
HB_IP[6]="2000::2"
HA_WG_IP[6]="fec0:1::a"
HB_WG_IP[6]="fec0:1::b"
WG_NET[6]="fec0:1::"
HA="ip netns exec ha"
HB="ip netns exec hb"


test_wg()
{
        wg genkey | tee left_private.key | wg pubkey > left_public.key
        wg genkey | tee right_private.key | wg pubkey > right_public.key

        $HA ip link add wg0 type wireguard
        $HA ip addr add ${HA_WG_IP[$IN_V]}/${MASK[$IN_V]} dev wg0
        $HB ip link add wg0 type wireguard
        $HB ip addr add ${HB_WG_IP[$IN_V]}/${MASK[$IN_V]} dev wg0

        $HA wg set wg0 private-key ./left_private.key listen-port 56781 \
                peer $(cat right_public.key) allowed-ips ${WG_NET[$IN_V]}/${MASK[$IN_V]} \
                endpoint ${HB_IP[$IN_V]}:56782
        $HA wg
        $HB wg set wg0 private-key ./right_private.key listen-port 56782 \
                peer $(cat left_public.key) allowed-ips ${WG_NET[$IN_V]}/${MASK[$IN_V]} \
                endpoint ${HA_IP[$IN_V]}:56781
        $HB wg
        $HA ip link set wg0 up
        $HB ip link set wg0 up
        $HA ping ${HB_WG_IP[$IN_V]} -c 4 -i 0.1
        $HB ping ${HA_WG_IP[$IN_V]} -c 4 -i 0.1
}

netns_1_net.sh
test_wg
modprobe -r veth
ip -a netns del

Update:

When removing a netns before removing the wg interface, the wg_netns_pre_exit() is called first.
But the peer's dst cache is not removed. So later in netdev_run_todo() the
function will be hung at netdev_wait_allrefs(dev) as dev->priv_destructor(dev) 
runs later, the peer's dst cache could not be cleared and there is still a reference on the device.

The following fix works.

diff --git a/drivers/net/wireguard/device.c b/drivers/net/wireguard/device.c
index 551ddaaaf540..c370854c76eb 100644
--- a/drivers/net/wireguard/device.c
+++ b/drivers/net/wireguard/device.c
@@ -407,6 +407,7 @@ static void wg_netns_pre_exit(struct net *net)
                        mutex_lock(&wg->device_update_lock);
                        rcu_assign_pointer(wg->creating_net, NULL);
                        wg_socket_reinit(wg, NULL, NULL);
+                       wg_peer_remove_all(wg);
                        mutex_unlock(&wg->device_update_lock);
                }
        }

Jason's fix: https://git.kernel.org/pub/scm/linux/kernel/git/zx2c4/wireguard-linux.git/commit/?id=5e65f2741

Need to wait for Jason post the patch to netdev.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (new packages: kernel), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2022:3907