Used Nebula to build a cross-cloud Nomad cluster, very underrated and does 99% of what you'd want from Tailscale.
I actually use https://defined.net for a managed Nebula experience and it makes everything super easy to get going and the team is super helpful with the few issues that I have run into. The free tier is super generous with up to 100 hosts for free and you don't need a credit card to get started. I highly recommend checking it out.
I don't know why it seems to be so far below the radar in these comparisons / conversations. Perhaps the Tailscale marketing is just that good :)
EDIT: my bad, they have an Android client
https://play.google.com/store/apps/details?id=net.defined.mo...