Validation, Subforms and Note Fields

We are attempting to put some validation on a few Subforms on a fairly large subform as the dropdown values are conditionally populated based on other fields in the form.

As a protection against any edge case or bugs we might discover after this goes into use, we where hoping to add someValidation of form submission workflow in order to go over the form and check everything is valid before it is submitted. This is working for a lot of the fields on our form but the Subforms are providing us with some difficulties.

Namely: we cannot put an inline alert on anything around this?

We have tried the following but are getting different errors as a result. We would love to know if there are any strategies that will work as surely "Needing to put error messages against Subform data cannot" be an outside requirement?

Thing we tried.

Reason it didn't work.

Calling an inline alert against the form itself.

"Inline alert task cannot be applied on [Field_Name] field".

Calling an inline alert against the particular value that may be wrong in the Subform.

"Inline alert cannot be applied on sub fields".

Setting a Notes fields in proximity to the Subform and setting the content for this with our error message.

"[Field_Name] is a notes field and cannot be updated"
We have updated notes fields before (outside of validation) to includes proactive instructions so we presume this is to do with this being done specifically in a validation context?

Calling an inline alert against the same Notes field to see if would appear.

"Inline alert task cannot be applied on [Field_Name] field" again.

We don't really want to do these all as pop up alerts as the form is quite large, there's a lot to check and a window that they have to close before making changes isn't going to be leave them with any reference for what they need to correct. However, at the moment: if any of our Subforms are invalid and everything else is fine: they just get the message saying "Invalid entries found. Rectify and submit again." with no context.

Someone must have had to do this before, right?