Is there a way to make a linked field be single selected instead of multiple selected? It is needed to avoid errors in formulas and user (forms) experience.
At this time, it is possible to add a soft constraint to only allow one record to be linked in a linked field, by unchecking the “Allow linking to multiple records” checkbox in the field configuration.
However, since it’s a soft constraint, the field is still considered to be multi-valued from any formulas that read from that field, as it’s not guaranteed to be single-valued. We may introduce a hard-constrained, single valued link field type at some point in the future.