SUMMARY fulltext search for "Å" with okular in https://arxiv.org/pdf/1301.2134.pdf yields no results, even though I got the character out of this document by selecting and copying. Searching for the same character in the same document in evince or qpdfview works as expected.
A possibly relevant merge request was started @ https://invent.kde.org/graphics/okular/-/merge_requests/339
Git commit d112682611cd38fe7f28943f688648b5862c7582 by Albert Astals Cid. Committed on 21/12/2020 at 22:32. Pushed by aacid into branch 'release/20.12'. Make search work on documents that describe Å as A + ◌̊ M +23 -0 autotests/searchtest.cpp M +16 -1 core/textpage.cpp https://invent.kde.org/graphics/okular/commit/d112682611cd38fe7f28943f688648b5862c7582