Lookup fields can be utilized as a portal table, but there is a certain configuration in Airtable that needs to be set up for the lookup field to appear in the list of valid portal tables. The lookup field must be trying to show a linked record field. This is an example of a lookup field configuration.

The lookup field is established in Table 1, which is linked to Table 3, and Table 3 is linked to Table 2. Within this field, the lookup is based on the linked record field to Table 3, and the displayed value is the linked record field that corresponds to Table 2 in Table 3.