The author ran several similar setups in production for years and has seen a lot of problems and strange failure modes.
This project aims to solve a lot of those (at least for the author), it might also be useful for others :)

Key features:

Images built via CI
WiFi connection support
Raspberry Pi (Arm64) compatibility
USB flash drive, USB SSD, etc. compatible
aarch64 mode for Raspberry Pis (significant performance improvements over armv7/32bit ARM)
Read-only filesystem handling (no more broken SD cards)
Configurable cache clear functionality
HTTP watchdog (website needs to send heartbeat messages via XHR/AJAX to localhost)
Force specific resolution (1080p on 4k screens, broken EDID, etc.)
Hard NTP handling (will wait for NTP at boot)
SSH support
VNC support
SSH tunneling support (for remote-access without port-forwarding, etc.)

Planned features:

PC (x86) compatibility
Raspberry Pi PXE/network boot support
Network connectivity watchdog (configurable ping, etc. timeout)
Automatic reboot at specified time

Security considerations:

Autossh does not check SSH host keys. This is okay-ish as long as the target server only allows tunneling, nothing else.
nginx/PHP are allowed to use sudo/NOPASSWD (because it needs to query the VideoCore, manage service, etc.), more priviledge seperation would be nice
due to the skeleton mechanism, the system has some ... creative permissions. some cleanup required.

Inspirations / Other Kiosk-OSes: