Just received ver.18.27 update and installed successfully.

I have also done the update and now have a "Test" tab in the watch submenu in the Connect app. Another thing I noticed is that the menu for the individual heart rate is completely messed up. But maybe this is more related to the new Connect app? Who knows.

Same.  No release notes.

Come on Garmin, until the last few months you ALWAYS released a firmware with a forum announcement and release notes.

The last 2 or 3 releases have had neither.

Same here. Haven't noticed any difference from 18.26 yet.

Just got the 19.12 this morning for my F255.

That's 3 update in a week..

Only difference I have seen which I really like, is that notifications with images now show that image on the watch. So someone sends you a sticker on whatsapp, or the ring doorbell spots someone at the front door, it shows that. Will need to test it with more images to see what exactly it shows. 

Garmin-Sierra any information about this?

A sticky has now been posted.

What is the meaning of "factory processes" in their Change Log ?

I hope it means they have streamlined the firmware update process to be more robust. Traditionally, some watches get issues with battery drain or missing sensors after upgrades.

I remember many years ago Ray Maker commenting about these exact updates as merely being what they say, i.e. 'supporting fabrication' of a slightly altered hardware version of the watch. For example, if a supplier of some small chip (like a voltage regulator or logic chip) has ended an older version, or there is a change of supplier, and the new chip needs a different 'setup' or 'reset' procedure, then all future watch firmwares will need to handle both hardware versions.

The above was a simplified explanation I concocted from memory of Ray's comment and my own limited knowledge of low-level hardware programming, but I believe it touches reality...

Please give us Training Readiness :)