ePub compatibility issues are one of the worst parts of having a Kobo reader. I genuinely miss my Kindle and its simple but reliable MOBI format. At least there everything worked
I’ve switched to kobos (Clara HD) and I’ve had to for years. It’s chugging along (had to 3d print a replacement power button a couple months ago), I can run koreader no problem and use calibre with the kobo plugin. And the default rendering engine in kobo’s firmware does actually typeset the text: no ragged edges!