Oh, I've very much heard of OpenWISP. The problem is I have a heavy bias against Wi-FI (ironic given the forum we're on, I know) & more so with mesh. Gimme good ol'Cat 6+ any day of the week.
Obligatory 'the cloud' is merely some one else's computer(s). You've heard of TailScale, yes? HeadScale is the F/OSS self-hosted control server to replace a TailScale server side/account. There's also 'Netbird' but I doubt very much either of their clients will sit on a stock AR300M with its limited 16 MB flash storage. Good thing I've got something for that: