I keep my RE allocation in an ETF, REET, due to being a renter and also not in the position to be a landlord.
Fees are low, and I purchase shares commission free on TDA. Buying in chunks every couple of weeks per my investment policy.
It tracks a global reit index if you are into that. I am interested in both commercial RE and global allocation, so it is perfect for me.
Not sure the diversification is necessary though, a total market index is sufficient for most. For me it is more of a personal interest with a side diversification benifit. I get a kick out of coming home amd telling my wife that we bought some more real estate that day.