Hi Tom & welcome to the community! Unfortunately, currently Airtable only supports text comparison filters when using linked records as you have seen.
Theoretically you could work around this limitation by using a single/multi-select field alongside the linked record field, & using an automation to set the selectable options & selected value of that field whenever the linked record field changes. This would need to be done via a scripting step in the automation.
Depending on your use case, you may or may not need to worry about the reverse. Meaning, automatically setting the linked record field value when the single/multi-select field changes. If just using the select field as a reporting filter, then this reverse scenario shouldn’t be needed.
Hope this helps!
Thanks for the clarification. At least I know I was not missing something
It does seem like a strange limitation in AirTable - since using Linked tables to manage the content in a selection list is so much more powerful and flexible than relying on the normal Select fields