Best tea alternatives?

I love tea (white no sugar). I'd just bought load of high quality loose leaf tea (due to somewhere closing and clearing stock) before getting diagnosed and told to avoid caffeine. Well I was told when prescriber remembered...

On methylphenidate if I do have caffeine I'm prone to very reactive heart rate and sometimes impact on mood and thinking so switched to decaf

I'm now getting the same issues on decaf, especially heart rate.

There doesn't seem to be a standard for decaf and I understand it's more reduced than removed but seems rather hit and miss.

Do any tea afficianodos out there have recommedations that they switched to please?