Hi,

You are probably looking for https://developer.matomo.org/guides/getting-started-part-1

Great thank you @Findus23

When looking at fixes should I target the 3.x or 4.x branch as not sure what the plans are in regards to PHP minimum version for each branch

Any major change should be made against 4.x (minimum PHP version 7.2 or 7.3). If it is a bugfix that should also be applied in the next bugfix release also create it against 3.x (minimum 5.5.x)

BTW bit hidden but there are more "in depth" docs here: https://developer.matomo.org/piwik-in-depth . For 3.x we would indeed mostly only accept regressions or important bug fixes as we're started working on 4.x a while back as @Findus23 mentioned. Re communication ideally we communicate on an issue or PR. Email we're trying to avoid when possible but could switch over to email if needed later. We otherwise also have a category for this purpose in the forum if there are particular questions: https://forum.matomo.org/c/plugins-platform

I'll close the issue for now but feel free to comment on the issue and we can further discuss.