Well hello neighbor, hahaha.
I'm old school in some ways, I still use bulbs. When I was getting Cosmo started I had to change the setup his original owner brought him in. He came to me in a little 5(?) gallon tank with a UTH on the bottom and a UTH on the side. So, I put him in a tiny tupperware I already had lying around, positioned that strategically over the existing UTH in the tiny tank and set a heat lamp on the tank screen. I kept the side UTH unplugged. This allowed the UTH and lamp to create an ambient temp with a hot spot using thermostats.
After a week of making myself forget he was there (obviously not literally, it took willpower to not handle the little cutie) besides temp checks and fresh water, I offered
and he ate. It worked, he kept eating and I stuck with it.