Hi,
I use https://www.manager.io/releases to see what changed since last version, and I only see last updates since May 15th, but I updated the software 2 times since then.
Is there any other website I can read to have the changelogs?
Thanks
I would not depend on the releases information at all. Manager even within a day can undergo many changes, often fixing things that it may just have introduced, experimented with, etc. There is no roadmap, not a real maintained releases page, etc. Best is to often visit the forum to see what is going on. If you use Cloud it automatically updates versions sometimes to the annoyance of users as all of a sudden things may work differently.
Would be really meaningful if the release notes would identify the versions with significant changes only. This could be the motivation to update Manager. 
That would only make sense with stable releases, but new features usually bring bugs. So you either keep updating constantly, or eventually risk something breaking.
Manager is fine for many small businesses, and we use it that way. It is also a good tool for us to train entrepreneurs in bookkeeping, accounting discipline, and financial reporting. Resulting in better understanding of their business and performance.
But for our own core accounting, we prefer larger, established providers like Sage or Oracle, with roadmaps, support, and long-term continuity.
Manager has real value. The trade-off is constant change.
Release notes for stable releases and enhancements could be fantastic, yes. On your other points the constant change etc can impact the free versions of Manager rather than the paying subscribers because reading stuff like mentioned here Email error sending invoices - #11 by maryeodea. strikes fear into me not knowing what the updates are going to deliver. I think some people understand the development risks and throwing it out to the masses pulls problems out pretty quickly but maybe somehow there could be some shielding / insulation for the Cloud / Server Editions?
This is inaccurate. There is virtually no difference between free desktop and paid for Server and Cloud Editions. As far as upgrades/updates are concerned these are automatic for Cloud users and user-driven for Desktop and Server users. You could argue that Cloud users benefit but also suffer quicker from changes because they get done without their control.
I repeat “..new features usually bring bugs. So you either keep updating constantly, or eventually risk something breaking…”
There is no benefit in the release notes as the changes are too often.