I am trying to setup a TO with 19.07 from scratch, but when it boots up, uhttpd is not running and is waiting the the openssl step to complete. It stays in the state forever. A workaround seems to be to perform a first boot from 18.06 to get the key file generated and then upgrade to 19.07.
root@OpenWrt:~# ps -w | grep uhttp
3265 root 1220 S /bin/sh /etc/rc.common /etc/rc.d/S50uhttpd boot
3372 root 3568 S /usr/bin/openssl req -x509 -sha256 -outform der -nodes -days 730 -newkey rsa:2048 -keyout /etc/uhttpd.key
4152 root 1064 S grep uhttp
could be that the openssl key generation hangs during maiden boot since there is almost nothing running at that time in the system and thus having a hard time to gather entropy and to generate certificate.
Mvebu is especially difficult target on entropy perspective as the WiFi driver does not generate entropy to the kernel pool, like e.g. ath9k and similar drivers do.
I bought a chaoskey entropy key for my wrt3200acm and introduced the drivers for it to OpenWrt. That helps a lot.
You might try generating the key manually later, after the boot process has completed. Jill the uhttps keygen process and possibly uhttps, wait a few minutes, and restart uhttpd to generate the keys.