Hey,
Since a few weeks every time I try to open a file dialog on Firefox it completely crashes and my xdg-desktop-portal-gtk services crashes as well with a core dump.
I cannot reproduce this on Chromium or other software making use of the same xdg portal.
I’m using sway as my DE and here is my NixOS config: GitHub - jocelynthode/nixos-config: My NixOS configuration
Any help or hint on where to start investigating to determine what’s causing this issue would be appreciated 
I stumbled upon this post while trying to debug the same problem and just wanted to post my solution. After some experimentation (And trying much more complicated stuff) I realized that this was limited to one user account on my machine → It is a user configuration issue, not a system wide issue → Deleting the ~/.config/dconf folder and restarting Firefox fixed it.
Not sure what lead to it being broken, probably some embarrassing mistake on my part, but maybe this helps someone who has the same issue.
I’ve seen a bug that did this to a friend: if your folder contained a json file, then firefox/nautilus/dolphin would crash because of tracker bug
Crash when opening folders with js or json that have content (#3273) · Issues · GNOME / Files · GitLab
Bug #2047737 “Nautilus crashes when opening folders that contain...” : Bugs : nautilus package : Ubuntu
Might not be it since chrome works though…