The export inputenc-luatex-utf8_pdf5_texF has been succeeding for a
while and was likely fixed by a TeX Live update. Compiling manually
and looking at the output looks good.
# before an ERT nested in a Description list:
export/export/lyx2lyx/lyx_2_3_test2_lyx(16|20)
-# New problem with TL18: endless loop?
-# ! TeX capacity exceeded, sorry [input stack +size=5000].
-# rsp.:
-# > ! Undefined control sequence.
-# > l.1 à
-export/export/latex/inputenc-luatex-utf8_pdf5_texF
-
# nonstandard tests failing for unknown reason:
export/templates/Obsolete/ACM_SIGGGRAPH.*_pdf5_(texF|systemF)
export/templates/Articles/R_Journal_(dvi3|pdf[45])_systemF