.local here too.
Any new domains I build I'll be using ".internal".
When i had my macs put in last summer we had issues with my .local domain name.
.local here and most schools unless part of a bigger group tend to be the same.
I have seen .int used too and .lan
If I was to build a domain up again I would use the same as web and then when users are in and out of the LAN if we allowed it something could be accessed via the same URL, no confusion then.
I'm not sure why, but our LEA structure uses 'schXXXX.somerset.gov.uk'. The networks are not linked via AD etc... There is a WAN but schools are basically silos on it.
.local here. No issues (touch wood)
Had Apple issues in the past but cant for 100% say due to .local
Microsoft's best practice used to be that your AD domain was different to your external so hence .local and .internal domain names. In recent years they have changed their mind and "Microsoft strongly recommends this option" of using a subdomain of your external domain name, and using split brain DNS you don't have to make the name publicly available.