Modern small engines can tolerate ethanol fuels. Older models are likely to have substances in their fuel lines, gaskets, plugs, tank linings, etc. that was designed with pure hydrocarbon fuel in mind and which adversely reacts with ethanol.
Interesting, thanks. My lawn tractor is a 1992 MTD model so I’m not sure about it. Service guy told me “never sell it, they’re not made like this anymore”.