Actually, Daniel, your mention of "upgrading" to LXQt has me wondering whether or not you took an LXDE version and then upgraded to an LXQt version(unsupported by Lubuntu, officially) without cleaning up all the old LXDE/GTK stuff. This could certainly lead to you using pcmanfm rather than pcmanfm-qt or otherwise using some app or apps that use GTK2, which everything seems to point to being the problem. LXQt doesn't use GTK-anything, so it should entirely be a non-issue.
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1782984 Title: PCManFM freezes with Assertion `!xcb_xlib_threads_sequence_lost' failed when clicking on a file or folder in 18.04 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/pcmanfm/+bug/1782984/+subscriptions -- ubuntu-bugs mailing list firstname.lastname@example.org https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs