My wife and I have used GnuCash for 20 years. We used Quicken before that. Like GnuCash way better since it is actually double entry accounting. The major limitation of GnuCash is that it is not concurrent. So to people cannot be modifying the ledger at the same time. Not sure about viewing. It can be SQL database backed though I have never used that functionality. The other place where FOSS stuff probably lags is integrations.

Edit: Another area in which GnuCash is weak is basis tracking. Fine on accounting for gains and losses but for tracking the basis is limited. At least my version is. I am on 3.x which is the version in the repos of my near end of life Debian 10 distro and latest is 5.5. At least my version there is no way to show true returns either.