I've been having the same problem, Nautilus is unusably slow and crashes
relatively frequently in Sid since the 49.1 update.
I don't have most of the $XDG_DIRS but have configured them in
~/.config/user-dirs.dirs to try to workaround this issue (will report
back if things improve).
I purged all *tracker* packages as I assumed the problem lied there,
doesn't seem to have helped any.
# journalctl -b | grep -i nautilus | wc -l
on a system that has 5 hours of uptime reports 9000 matches.
Downgrading to libnautilus-extension4_49.0-1_amd64.deb
nautilus-data_49.0-1_all.deb nautilus_49.0-1_amd64.deb didn't help.
--
Simon John
