Custom Hostname Security Issues

After watching SpaceRex, I have have gotten myself a Synology NAS. This is for my family with Photos and Drive/Office. I was looking for a way to easily get into the different services. I came across aliases for the services, which is nice, but I want something even shorter. That is when I came across the Login Portal with Customized Domains. I see they end in .local, so I went to try it out. The first thing I get hit with was a security warning from Google Chrome. Is there any way I can remove that? I don’t want it to worry any of my family members.
Thank you!