It's safe to put a 4G/LTE Router as a DMZ to allow B one Wan port to handle internet?

I recently moved to a rural area with good 4G and Starlink coverage. I’m considering buying a B-One to bond both connections because Starlink occasionally slows down.

I mistakenly thought the TP-Link Deco X50-5G had a modem mode, but it doesn’t.
Is it safe to set this router to DMZ mode, or is that too risky?

There’s an option to buy the B-One 5G model, but my budget is tight. Any advice would be greatly appreciated, thanks.