Yup - you need to read / follow official Installation Instruction linked from Magisk home page; pay special attention to Samsung section... PWWhich of the things doesn't match the others?
To my great delight, I discovered a ROM for Samsung S5e (kminilte) with Android 9. Runs great - just can't get Magisk to work. Have tried alpha, Hitman's and JohnWu's new releases. Neither with TWRP nor with the direct patch of the boot.img (and flash via download mode) I get further - the flashing stops with every method when repacking the bootimage, without anything being flashed/patched. Do I have to mount anything manually or so? Honestly, I do not get through meanwhile - is there somewhere a working guide, which system requirements, which flash method and which other requirements should be given? Here in the thread I have bravely read along - as far as I know, I have also tried all the instructions, but no Magisk was installed. I do not need SNP, only ROOT and Hiding Root and the ExSD card module. I'm not sure, but I had the impression that Zygisk (first two alpha versions up to ...31 I could still completely flash via TWRP) brings my device into bootloop /freezing. Should we users (who do not have their own dev skills) rather wait until there is any beta or use an old Magisk classic or have I overlooked / not understood something essential?