I've just tested 5.51 (5.51.alpha1-202206100340), and "First Name" and "Last Name" seem to have disappeared from the import mapping options.
Tracking for #2858 (comment 75339)
I've just tested 5.51 (5.51.alpha1-202206100340), and "First Name" and "Last Name" seem to have disappeared from the import mapping options. I note that in the code (e.g. the mapFieldDataProvider function) they're now referred to as "first_name" and "last_name", but I can't find them in the field mapping dropdown (see screenshot).
The saved field mapping has reverted these fields to "- do not import -".
This prevents the import from running. I see the following error message when I try to click Continue to go past the Match Fields screen (step 2 of 4):
"Missing required contact matching fields. email(weight 15) first_name(weight 5) last_name(weight 10) (Sum of all weights should be greater than or equal to threshold: 30)."
I notice that "Organisation Name" is in the list, but Contact Type is definitely set to Individual in the first screen of the import process.