Comment 417 for bug 1887190

The solution has been found and should have been rather obvious in the first place... Just try a different distribution.

I decided to try out Linux Mint 20.1 and have been testing it for the past ~6 hours, completely stock (except for all updates installed), no kernel modifications or GRUB options and it works every time on bootup with the touchpad. I am rather surprised that such a relatively old kernel (5.4) works with this new-ish laptop. Perhaps this was why I was so falsely focused on having newer kernels available in a distribution in the first place.

I even tried 40 consecutive reboots whilst messing with the touchpad as the machine was booting and it still worked every time. Let it be known that the fix for the Lenovo IdeaPad 3 14ADA05 is to simply install Linux Mint. I have to imagine that other Ubuntu-based installs also work with this particular laptop, especially since it says "Fix Released" under Ubuntu and Ubuntu-related distributions.

As far as Manjaro goes, also let it be known that something was introduced after Kernel 5.9.16-1 which breaks the ability for the touchpad to reliably work with this laptop. My best educated guess is that something is loaded too early or too late during bootup which gets jumbled up at random. No idea what that could possibly be, but I hope that Manjaro devs might take note. I know that at least @Helmut Stult might still be looking in this thread.

I consider this fixed for my laptop :)