Installed after latest HS update: one machine refuses to boot (“too many corpses”), and the other refuses to go into cmd-R to permit restarting SIP via Term! What now??

This sounds scary. Why do you think it is TotalFinder related?

I’m rolling on latest High Sierra developer updates and didn’t encounter any issues. Also not hearing from other folks about something similar.

The last thing done before the issue was install TF, then turn off SIP to complete the install, then experienced the issues, so unable to go forward. It might just be the HS updates, but have now no way to tell…

First, try to see what bootable drives do you have available when holding just OPT during reboot. This should show you recovery HD partitions as well. It might be just a confusion during booting that CMD+R fails to select the correct partition with working recovery HD.

Second, you might want to consider installing a new macOS on a separate external drive, USB stick with 8+ GB should work as well. This should create associated recovery HD partition on that external drive. Then you can use it to turn SIP on/off. Also that newly installed system can be used for inspection of what went wrong.

Will try opt-key first, thanks. Will report anything learned.

Finally got my 2008 Mac Pro to run, but in normal mode it still will not recognize that csrutil has been re-enabled (successfully, as reported by Terminal under Command-R). I’ve turned off the warning, but would like to know if there is another approach to try…
The Mac Mini will attempt a re-install of OSX, but then will again stay stuck on repeating instances of “too many corpses”…

What is csrutil status reporting in your Mac Pro Terminal booted in normal mode?

This might be related:

I’m on High Sierra 10.13.5 and Total Space and Total finder both seem to run normally. What am I doing wrong?