With GMT 6.5.0 released, now PyGMT supports three GMT minor versions, 6.3, 6.4 and 6.5, although old GMT versions may have some bugs and miss some features. Supporting multiple GMT versions is a big burden for us maintainers, so we need to decide our policy for the minimum supported GMT versions.

Here are a few options:

1. No policy, i.e., try our best to support the oldest GMT version, unless there is no way or very difficult to be backward-compatible
2. Follow SPEC 0's recommendations for Python versions (Migrate from NEP 029 to SPEC 0 #2863), and support for GMT versions to be dropped 3 years after their initial release.
3. Follow SPEC 0's recommendations for core package dependencies (Migrate from NEP 029 to SPEC 0 #2863), and support for GMT versions to be dropped 2 years after their initial release.

FYI, GMT usually has one release per year (https://github.com/GenericMappingTools/gmt/tags).

• GMT 6.3.0 was released on Nov 19, 2021
• GMT 6.4.0 was released on Jun 16, 2022
• GMT 6.5.0 was released on Jan 7, 2024