Yeah, dozens of us are using OpenWrt snapshots and everything works well.
The only noteworthy difference is that the stock firmware has WED enabled, so you’d need to enable that on the snapshots to get hardware acceleration for WiFi.
You can easily compile OpenWrt for the GL-MT6000. Someone even posted their custom builds with a newer kernel just yesterday.
You can no longer easily compile your own GL.iNet firmware though. I believe they shut down the builder because their Chinese user base were using it to bypass restrictions, which puts the company at risk.