OK, one more step done. Everyone on Masto.host is now running v4.0.
About half running v4.0.2 and half v4.0.1.
For the ones on v4.0.2 the upgrade is done (unless v4.0.3 is released ? ).
The others on v4.0.1 I will upgrade them in the next hours to v4.0.2. A small restart is required that will cause about 15 seconds of downtime.
If you run into any issues, please let me know. Thanks.