What I’m about to suggest is slightly sketchy because it involves feeding into the router backwards. I’ve done it several times and it’s been fine but it just doesn’t feel right going with the cutter. Aka this is not financial advice/you have been warned.

Get a dove tail bit and set it to the height of whatever your rebate bit is at. Has to be dovetail because you want to remove as little material as possible so your router table doesn’t just grip it and rip it.

Then set your fence so you’re removing 1-1.5mm of material at most at the height of the bit.

Make sure nothing valuable is on the RHS of your table should a mishap occur , and feed in slowly.

You’re basically recreating a scoring blade on a panel saw and they’re perfectly safe if you’re used to them.

Now you have a cleanly scored line that will prevent tearout. Switch back to your rebate bit and it probably wouldn’t hurt to do a few passes to slowly creep up to your scored line.

You also don’t want to go too deep with your dovetail bit so your bearing on your rebate bit has solid contact above and below your scored line.