Browse and open NAS-Files not working in Linux with rawtherapee

System: Linux Mint 20.3 Cinnamon, 5.2.7, 5.4.0-96-generic

RawTherapee: Version: 5.8
Branch: releases, Commit: 9a9e0acbf, Commit date: 2020-02-04, Compiler: cc 9.2.1
Processor: generic, System: Linux, Bit depth: 64 bits, Gtkmm: V3.24.2, Lensfun: V0.3.2.0
Build type: Release
Build flags: -g -O2 -fstack-protector-strong -Wformat -Werror=format-security -fPIC -Wdate-time -D_FORTIFY_SOURCE=2 -std=c++11 -Werror=unused-label -Werror=delete-incomplete -Wall -Wuninitialized -Wcast-qual -Wno-deprecated-declarations -Wno-unused-result -fopenmp -Werror=unknown-pragmas -O3 -DNDEBUG -ftree-vectorize
Link flags: -Wl,-Bsymbolic-functions -Wl,-z,relro -Wl,-z,now -Wl,–as-needed
OpenMP support: ON
MMAP support: ON

My NAS is not shown in Rawtherapee “Places”.
Nemo 5.2.4 shows it right in Network and “Bookmarks”
Other programms (LibreOffice) let me browse and open files on my NAS.
What can i do to browse and open files on my NAS with rawtherapee?