Crostini is a mixed bag; e.g. IIRC something in their stack breaks ptrace. I prefer to wipe and install a normal Linux distro. But, when it works it works, and I do use one Chromebook with Crostini.
ptrace works fine on crostini. The guest kernel has Yama enabled, which restricts it to root for boring security reasons. You can do your debugging at a root shell or turn the setting (yama/ptrace_scope) off via sysctl.