Old Kobo Aura H2O question on downgrading firmware

[sparklemotion]

Hi everyone, I have an old Kobo Aura H2O (2014 version) that still works great, but the page turns have been painfully slow which is why I don't use it much anymore. I recently noticed someone online saying they had the same issue and they downgraded the firmware on theirs and now it's back to being zippy. (A factory reset didn't help mine, and it also retains the newest firmware)

Has anyone done this with their Aura H2O due to it lagging? Can anyone please advise what firmware would be a good bet for me to downgrade to? I'm currently on the latest 4.38. I found a couple sites with older versions, but it becomes a bit confusing which one to safely download.