I can confirm as of today this is still an issue.  My internet dropped and my whole network went down, wired and wireless.  Spoke to someone from tech support who does not understand the difference between internet and a LAN and she kept telling me that you cannot have a LAN without internet. SMH

For what it's worth, here is my experience, which is slightly different from the others: 

I purchased eero for the sole purpose of using it as an "intranet" wired/wireless network router for a live sound mixer. I was able to successfully run the initial setup by joining my home network (connected to the Internet).

Once it was set up, I USED TO BE able to take the system anywhere and connect all devices to eero network without an Internet connection.

In other words, once it was set up, eero used to work fine as a standalone LAN router without any Internet. However, something broke in the last couple of years where WIRELESS network still works without any Internet, but it Ethernet network now only works if there is an Internet connection. 

I CLEARLY REMEMBER CONNECTING DEVICES VIA HARD WIRE WITHOUT ANY INTERNET (after the initial setup). I can't recall which version, but it was working in February 2020 right before COVID lockdown.

Please make it work again

I just had the most frustrating call with tech support. The person insisted that an internet connection was required for lan traffic and no other wireless router supported this functionality. 
 

I am so disappointed in this major design flaw with eero products (I just purchased a 3 pack of the 6 pros). The only reason I can even imagine that eero would intentionally disable LAN traffic is to sell the eero plus monthly subscription. Whoever at eero thought this was a good idea to break a product so you can sell an add-on is preying on customers that don’t understand the basics of networking. I will say that having your home wifi network tether off your phone (which is what I understand eero internet backup allows) is a very ingenious and useful feature - but it cannot come at the expense of breaking basic product functionality to create a sell-up path.  I was considering paying the monthly subscription before I had this experience of eero blocking lan traffic  now there is no way I will give extra money to the company  

Has anyone found a useful channel to voice these concerns (someone at eero that is empowered to undo this decision) as the tech support team is not equipped to have discussions on the inadequacies of their products 

I'm not very knowledgeable in this area, but my eero pro works when internet is not available.  I found out that my mobile phone just won't connect to LAN wifi when it doesn't have internet with mobile data on.  When I turn off mobile data, my phone can access the LAN content no problem.  On computers, it seems to work fine too.

What device are you testing the LAN 

I will do some testing and report back here in a few weeks.  I really hope the customer service rep I spoke with was wrong and this basic functionality actually exists. I noticed you cannot make any changes to the eero network without an internet connection (apparently there is no local connection to the “gateway” eero to access settings. That is a manageable deficiency as long as everything else functions as expected

soo... just got Eero Pro 6e , power & internet went out and LAN devices that should work w.o internet -- don't (ie printer, airdrop, misc smart home things). Software version 6.16.4-11... pretty useless to invest in the backup batteries for each Eero and system itself if it doesn't do a basic task of keeping home devices (that are also on battery backup) talking.... ancient Apple AirPort Extreme did it instantenously.

Also what the heck is with the range... advertised for 6000 sq ft but barely manages 4500.... really hope LAN issue gets sorted.. asap... otherwise it's going back :/