innernet VS gravity-sync

Innernet is a barebone alternative. https://github.com/tonarino/innernet

Very relatable! At first, I struggled for days trying to make Netmaker or Innernet functional for my personal home server (Raspberry Pi behind multiple routers). But then I stumbled upon ZeroTier, and everything worked seamlessly within a couple of hours. Tailscale was actually the next one on my list because I heard many positive things about it over at r/selfhosted (especially about headscale). However, I did not end up testing it after ZeroTier worked.

Not if you are running wireguard without any management client/server like Netmaker or innernet or any of the many others like them.

I use the GCP free instance as my innernet coordination server (Wireguard mesh vpn). Which is extremely low traffic.

Or why not the open source tool innernet? https://github.com/tonarino/innernet

I wonder if this might improve over a more modern transport, if you were using an IPSec VPN.

Wireguard is enabling us to re-think what's possible over a VPN. Here's an example of what I mean. The network stack is based on Wireguard, with https://github.com/tonarino/innernet providing the topology and identity provisioning.

Virtual Private Network: Innernet, MASQ

OR I could implement https://github.com/vmstan/gravity-sync as it's last commit was a year ago but users still seem to be using it.

I run the split DHCP approach for years without issues. Having only one PiHole with DHCP Server doesn’t give you a fully redundant system. I don’t use Gravity Sync myself, but their wiki covers this case with examples: https://github.com/vmstan/gravity-sync/wiki/DHCP-Replication

the github page has a really good walkthrough and explanation

I don't have anything add to your question. But I recommend installing gravity-sync if you're going to run two piholes. It will sync up DNS entries (among other things) automatically to the second pihole when you add a entry one of them. https://github.com/vmstan/gravity-sync

If you go the 2 pihole route, I strongly recommend Gravity-Synch. https://github.com/vmstan/gravity-sync

Run Pihole on both, if DNS goes down its painful. You can sync them with https://github.com/vmstan/gravity-sync