Whitelist and black list Failure

For those not being able to resolve this, please try

pihole checkout web fix/check_idn

which will disable support for international domains if the required extension is missing.

@DanSchaper Yes, this is DietPi on a RPi3 which is only running Pihole for its DNS service. I have noticed this error message too, but I don't know what to make of it. I now checked my other RPi3 running the stable version of Pihole, and it shows the same X-Header error message. Hence it does not seem to be related to Beta5.0, I may have to double-check my lighttpd config.

@tjamaa: installing php-intl ver. 7.3 fixed the problem apt-get install php7.3-intl
I am running dietpi as well.
@DanSchaper THX for support

Yep, the Whitelist and Blacklist pages are back!

The result of 'apt-get install php7.3-intl':

The following NEW packages will be installed:
  php7.3-intl
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 107 kB of archives.
After this operation, 335 kB of additional disk space will be used.
Get:1 https://packages.sury.org/php stretch/main armhf php7.3-intl armhf 7.3.14-5+0~20200202.52+debian9~1.gbpa71879 [107 kB]
Fetched 107 kB in 0s (113 kB/s)
Selecting previously unselected package php7.3-intl.
(Reading database ... 22515 files and directories currently installed.)
Preparing to unpack .../php7.3-intl_7.3.14-5+0~20200202.52+debian9~1.gbpa71879_armhf.deb ...
Unpacking php7.3-intl (7.3.14-5+0~20200202.52+debian9~1.gbpa71879) ...
Processing triggers for php7.3-fpm (7.3.14-5+0~20200202.52+debian9~1.gbpa71879) ...
Setting up php7.3-intl (7.3.14-5+0~20200202.52+debian9~1.gbpa71879) ...

Creating config file /etc/php/7.3/mods-available/intl.ini with new version
Processing triggers for php7.3-fpm (7.3.14-5+0~20200202.52+debian9~1.gbpa71879) ...
Processing triggers for php7.3-cli (7.3.14-5+0~20200202.52+debian9~1.gbpa71879) ...

I then went back to checkout core and ftl release/5.0, and the Whitelist and Blacklist pages appeared. Problem solved it seems.