That’s a limitation created by apple, not alt server. Granted you are using one of your three to use alt store, but you can skip using alt store if you don’t want auto refresh by just using the server to install your IPAs.
But Altstore does run on Windows, Mac and Linux (I use a helper script to run it on my home server)
These are all work around to Apple imposed limitations, it’s by no means perfect, but until Apple change their mind (or are forced to change their mind) your alternatives are jailbreaking (which I don’t think there are any public jailbreaks of the latest hardware/OS) or swap to Android (which I’m considering doing) or pay Apple $100 a year for your own dev cert with less restrictions.
But Altstore does run on Windows, Mac and Linux (I use a helper script to run it on my home server)
These are all work around to Apple imposed limitations, it’s by no means perfect, but until Apple change their mind (or are forced to change their mind) your alternatives are jailbreaking (which I don’t think there are any public jailbreaks of the latest hardware/OS) or swap to Android (which I’m considering doing) or pay Apple $100 a year for your own dev cert with less restrictions.