There is another interesting company in this space- Netmaker[0]. It's been getting a lot of traction in the homelab space- namely because it takes advantage of kernel wireguard, which is more performant than the userspace wireguard that tailscale uses.
There's https://zerotier.com, https://netbird.io, https://defined.net, https://github.com/tonarino/innernet and likely many more.