Here https://lists.gnu.org/archive/html/lilypond-devel/2019-10/msg00236.html I reported some problems, likely caused by ly_scm_write_string.
Once I'll be back from Salzburg I'll try to compile LilyPond against guile-3.0 with the patches linked above and the changes mentioned here: https://lists.gnu.org/archive/html/lilypond-devel/2019-11/msg00213.html Or, maybe you already have some insights? https://codereview.appspot.com/545450043/
