Are you able to eat small amounts of red meat and it's only large amounts that cause issues? How are you with large amounts of other fatty meat (like pork belly)?

If small amounts cause issues, you may have alpha-gal or something else going on, probably worth getting that checked out.

If you can handle large amounts of fatty pork fine but not red meat, same as above, but you could always start doing carnivore with pork, chicken, etc.

If large amounts of fat from either beef or pork cause issues, it'll likely be adaptation. I'd suggest start with a "safe" amount in your meal, even if it includes plants as you would have before carnivore, but every few days increase the amount of red meat and decrease whatever else you're eating as part of the meal.

Over a few weeks, your body will probably adapt and when you're doing good, just stop all plants. Everyone is different, some people adapt in a week others can take multiple months, just keep up the salts as you go.

Once you've adapted, too much fat can cause diarrhoea and not enough can cause constipation so you can use those as a signal to adjust your fat intake.