When updating adlists, to detect problems I review the logs and open a report with the list maintainer to remove invalid entries. This works well on domain only lists, however for new abp style lists the output mixes IP's and domains that are ignored eg:
[✓] Status: No changes detected
[✓] Parsed 0 exact domains and 54077 ABP-style domains (ignored 27 non-domain entries)
Sample of non-domain entries:
While the output is correct as the ips are non domain entries, abp lists actually support IP addresses officially. It would be more helpful if pihole stated something like ignored 7 non domain entries and ignored 20 ip addresses then listed the non domain entries as this can help detect problems and then improve the lists which helps everyone. Unfortunately pihole only lists 5 entries so it is easy for invalid entries to fall off the list and only ips be displayed.
If another line cannot be displayed for IP's another alternative solution would be to allow more than 5 (ie unlimited sample) of invalid domains in output if required so the fill list can be reviewed and monitored for issues.
Please consider this if possible as it would help improve lists.