You can also operate the Shelly without an internet connection hur Shellycloud. E.g. with a Raspberry with Grafana or Iobroker or something. The Shelly does not store any values but sends its values cyclically or, in the case of thresholds, to current locations.

The standard firmware of the Shelly H&T does not store any values, you can only read out the current value.
However, Shelly is quite modding friendly, so there may be alternative firmwares that allow recording.

For long-term recording I am very satisfied with the TFA Klimalogg Pro.
It stores the data for several years without having to read it out, but it is a bit more expensive.