How about OpenWRT? It appears it has support for MPLS[1], IS-IS[2], and VXLAN[3]. Where VXLAN appears to even have a LuCI component[4].

[1] https://openwrt.org/packages/pkgdata/kmod-mpls

[2] https://openwrt.org/packages/pkgdata/frr

[3] https://openwrt.org/packages/pkgdata/vxlan

[4] https://openwrt.org/packages/pkgdata/luci-proto-vxlan