Dnsmasq startup error

General
1

If /etc/pihole/black.list doesn't exist (no exact match black list entry), dnsmasq gives an error at startup:

May  4 20:21:36 dnsmasq[2764]: failed to load names from /etc/pihole/black.list: No such file or directory

This list is activated, by default in /etc/dnsmasq.d/01-pihole.conf

addn-hosts=/etc/pihole/black.list

workaround:
Create /etc/pihole/black.list, containing at least one blank line/

see also this error, already solved by @DL6ER.

2

What is not clear to me here - is this just a cosmetic issue (it logs this error) or is it actually severe (the service doesn't start)?

3

It is just a cosmetic issue.