I’ve solved my issue, but unfortunately, I wasn’t able to precisely pin down the cause.
My hunch is that I might have misconfigured my /etc/dhcpcd.conf file, as described here.
I went down the rabbit hole of trying to change these settings while debugging my connection failures, and that might have been premature. Reverting those changes, and then doing a full sudo reboot from the command line was enough to get Tor fully bootstrapped again.