Welcome to the community, @David_Short!
I’m assuming you’ve already created a linked record field between your two tables, so you can link multiple issues to each individual asset?
After that, Airtable makes the rest of the setup process unnecessarily complex:
First, you have to create a rollup field in your Assets table that points to the Date field in your Issues table. Use the formula
Then you have to go back into your Issues table and create a lookup field that looks up the rollup date field that you just created in your Assets table.
Then, while still in your Issues table, create a new formula field that compares the date of that particular record to the lookup field that you just created. If the 2 values match, then the formula should result in the Comments field for that record. (If the 2 values don’t match, it should result in nothing.)
Then, back in your Assets table, create a new lookup field that looks up the new formula field that you just created. That will show you your most recent comment.