How to get S2 L2A data harmonised through time

Use Sentinel Hub API, configured with harmonizeValues option.

Oh ok, but I need original image format, not tifs.

Using Sentinel Hub you can access L2A data directly, as they are. Check this example:

Examples for S2L2A

Use these CURL and Postman examples to access atmospherically corrected Sentinel-2 L2A data with Sentinel Hub API.

You mean to process it from L1C? Or to be able to download ready-to-go one?

this is a sad news, but thank You for the information

Then there is no other option than handling the differences between baseline versions on your side, as there does not exist a repository with new data with old-baseline-values.

btw… did L1C change as well in feb 25th? because using Sen2cor with baseline 3.00 did not fix the problem with different values.