Sorry for not responding earlier, but I have to admit I simply wasn’t sure anymore about this.
However, in the meantime I remembered the information from a trustable Fairphoner and /e/ user according to which due to the partnership between Fairphone and /e/, firmware patches and changes get sent on to /e/. Actually a current issue with the FP3 reminded me of that: FP3 users currently report about problems with automatic brightness – both under Fairphoner OS and /e/OS (at least I myself have the same issue under /e/OS). The issue arose from Fairphone’s attempt to actually improve brightness because users used to complain about too strong brightness even at the lowest level.