D'oh - I should have started there, thanks Gizmo! Cleared headers/footers, switched to PHP 8.1 (the highest version my host currently provides), and things came up as expected. I'll re-add the header/footer items one at a time to see where it broke.
EDIT: spoke a bit too soon, Control Panel wouldn't open. Will do some troubleshooting on that front.
Last edited by toner; 08/31/2024 3:18 PM.