Here's an email Google sent me during the night:
(right-click then "View Image" then zoom in so you can read it).
Seems Google's really determined to profit as much as possible not only from mining our data and serving us ads, but also by charging for things it so far provided for "free" (ie, for no payment besides access to our data).
So, if you upload a ton of pictures to Google Photos, better get ready to start paying for additional space (unless you are on an "unlimited" account, but seems those too are getting more expensive / harder to get).
If anyone knows of a good/free/convenient alternative, please post below. TIA.
Here is the blog which is slightly easier to read: https://blog.google/products/photos/storage-changes/
I really like Google photos - it works very well both on the app and in the web browser.
The API is appalling though - it is probably better to use google takeout that attempting to download your photos with rclone if you want them with metadata intact.
I can't say I'm surprised about getting rid of free storage. Storage isn't cheap. 4 Trillion photos is a lot and 28 billion new ones a week is inconceivable! At 1 MB per photo average that is 28PB a week! (or 370 Gbit/s if you prefer).
Thanks for the thoughtful, detailed comments as usual.
My peeve with Google is that they are not losing money, on the contrary: they are making money hand over fist. The least that they should do is to keep the initial arrangements that gave them total access to our data (which allowed them, at least in part, to make all that money)
So, I will probably use Takeout to migrate my photos, along with everything else.
I'm right now experimenting with NextCloud: it's free (both as in beer and as in freedom, and also as in "free from Google's prying eyes"). Right now I'm using one of the free providers, but my plan is to self-host it in a VPS -- turns out I can rent a VPS with a cheaper cost-per-GB than paying Google for the an "expanded" 100GB or 200GB One plan).
I will post about it in a new topic.