See the generic description. This mainly makes a place to discuss aarch64-specific issues for ZHF.

As of https://hydra.nixos.org/eval/1430755, there are 263 aarch64-specific failures (here the exact criterion is: never succeeded in the trunk jobset on aarch64, is currently succeeding on x86_64, is not broken only due to failing dependencies):

• a2jmidid
• aegisub: bundles luajit, needs marking x86-only
• aften
• aircrack-ng: calls SSE builtins
• altcoins.go-ethereum
• ams-lv2
• angelscript_2_22
• ao
• artyFX
• atlas
• audacity
• avy
• awless
• bcachefs-tools
• bcftools
• beignet
• betaflight
• blackmagic
• bonfire
• bootil
• bowtie2
• bud
• buildbot
• c3d
• cde
• chez: x86 compiler
• cl
• clisp
• coyim
• cxxtools
• deadbeef
• devpi-client
• dgraph
• distrho
• doodle
• dwarf-fortress-packages.dwarf-therapist-original
• eduke32
• eid-mw
• emulationstation
• enlightenment.efl
• eq10q
• ezquake
• firebird
• firebirdSuper
• flashrom
• freerdp_legacy
• fribid
• ghq
• gitAndTools.ghq
• glucose
• gmp4
• gnustep.libobjc
• go-ethereum
• go_1_8
• gocryptfs
• gogs
• gprolog: compiler without aarch64 support
• gravit
• gromacsDoubleMpi
• gromacsMpi
• grub2_xen
• gsl
• haka
• hardinfo: needs upgrade, latest tag is from 2009 but there's recent activity in git
• hdf4
• hound
• hping
• i7z
• imatix_gsl
• imv
• inform7
• ipfs
• john
• kbfs
• kcov
• kitty
• kiwix
• kubernetes-helm
• lean2
• lenmus
• lensfun
• libagar_test
• libantlr3c
• libb2 (libb2: 0.97 -> 0.98 and fix build on ARM #40362)
• libibverbs
• liblbfgs
• libretro.desmume
• libretro.dolphin
• libretro.mame
• libretro.mupen64plus
• libretro.parallel-n64
• libretro.ppsspp
• libretro.reicast
• libretro.scummvm
• libsForQt5.qca-qt5
• libsForQt510.qca-qt5
• libsnark: has x86 inline assembly
• libstdcxx5
• linuxPackages.evdi
• linuxPackages.openafsClient
• linuxPackages.sysdig
• linuxPackages_4_14.evdi
• linuxPackages_4_14.openafsClient
• linuxPackages_4_14.sysdig
• linuxPackages_4_15.sysdig
• linuxPackages_4_4.bbswitch
• linuxPackages_4_4.openafsClient
• linuxPackages_4_4.rtl8723bs
• linuxPackages_4_4.sysdig
• linuxPackages_4_9.evdi
• linuxPackages_4_9.openafsClient
• linuxPackages_4_9.sysdig
• linuxPackages_hardened.sysdig
• linuxPackages_latest.sysdig
• linuxPackages_latest_xen_dom0.sysdig
• llvm_35
• looking-glass-client
• ltrace
• luaffi
• lxdvdrip
• meshlab
• metersLv2
• mimetic
• minetest
• minisat
• mitscheme
• mitschemeX11
• mixxx
• mkcl
• mongodb
• mono48
• mono50
• mono54
• mplayer
• mps
• mupen64plus
• muscle
• mysql55
• nanoflann
• neovim-unwrapped
• neuron
• neuron-full
• neuron-mpi
• non
• nova-filters
• nvidia-texture-tools
• obs-studio
• ogre1_9
• open-wbo
• openbabel
• opencollada
• opencolorio
• opencpn
• openlibm
• openmvg
• openmvs
• openspades
• palemoon
• pgf_graphics
• picoc
• pjsip
• plink-ng
• plugin-torture
• pommed_light
• pond
• posterazor
• primusLib
• prometheus
• protobuf2_5: 2.x doesn't support aarch64
• psi
• python27Packages.binaryornot
• python27Packages.cherrypy
• python27Packages.imread
• python27Packages.joblib
• python27Packages.neuron
• python27Packages.neuron-mpi
• python27Packages.pandas
• python27Packages.pyamf
• python27Packages.pytorch
• python27Packages.scikitlearn
• python27Packages.scrapy
• python27Packages.vmprof
• python36Packages.bayespy
• python36Packages.binaryornot
• python36Packages.cherrypy
• python36Packages.imread
• python36Packages.joblib
• python36Packages.neuron
• python36Packages.neuron-mpi
• python36Packages.pandas
• python36Packages.pyocr
• python36Packages.pytorch
• python36Packages.scikitlearn
• python36Packages.scrapy
• python36Packages.vmprof
• qdigidoc
• qt5.qtwebengine
• qt510.qtwebengine
• qt59.qtwebengine
• qtpfsgui
• qtractor
• quantumminigolf
• radare
• rethinkdb
• rkrlv2
• rocksdb
• rocksdb_lite
• rucksack
• sbcl
• serfdom
• setbfree
• simplescreenrecorder
• slade
• softether
• softether_4_18
• softether_4_20
• sorcer
• spidermonkey_1_8_5
• srelay
• stag
• stella
• stepmania
• supercollider
• supercollider_scel
• sysprof
• tdesktop
• tennix
• terraform_0_8
• texstudio
• textadept
• the-powder-toy
• tightvnc
• tome4
• torch
• trezord
• tup: needs upgrade, upstream now has aarch64 support
• twister
• uhub
• uim
• unicon-lang: x86-only compiler I think
• v8_3_14
• v8_3_16_14
• v8_6_x
• vapoursynth
• vboot_reference
• vc
• vc_0_7
• voxelands
• wavegain
• welle-io
• x42-plugins
• xe-guest-utilities
• xfce.xfce4-battery-plugin
• xfce.xfce4_battery_plugin
• xfce4-12.xfce4-battery-plugin
• xfce4-12.xfce4_battery_plugin
• xgboost
• xmlrpc_c
• xonsh
• yap
• yarp
• yate
• zam-plugins

(I'm re-using this as a scratchpad for some notes on why the packages are failing; that is for the unticked "needs marking x86-only" ones I just haven't got around to writing a patch yet, feel free to be faster than me to commit).