This is probably due to an outdated version of AppImageLauncer (v2 was released in 2020).
Related: AppImageLauncher support - #10 by FritSau
Tested with v3 from 2025 , which works.
v2 probably doesn’t support zstd yet (needs xz). The older xz is about 5 times slower during startup, which is relevant for the large number of files in Fritzing.