https://www.sjoerdlangkemper.nl/2019/05/22/logging-dns-requests-with-internet-sharing-on-macos/ https://www.reddit.com/r/osx/comments/3tsu01/is_there_a_way_to_log_all_dns_queries_on_osx/ Or set up a DNS forwarder or DNS server set up to forward, and log the traffic there.

Depending on your particular level of familiarity with programming... https://developer.apple.com/swift/ https://developer.apple.com/swift/resources/ https://www.apple.com/swift/playgrounds/ There are books and courses around, as well... https://www.raywenderlich.com

Apple shifted the certificate requirements with those releases, and some vendors—reportedly GoDaddy, GlobalSign, Certigna, and WidePoint—got caught out by the requirements changes. https://sslmate.com/blog/post/apples_new_ct_policy Check with your certificate vendor for a replacement certificate, or switch to LetsEncrypt certificates.

I'd expect the app to be running in what amounts to a simulated iPadm analogous to what happens to apps running in an Xcode simulator. Few iOS or iPadOS apps are even going to know what to do with a Mac. Which means the device report makes sense. Pragmatically, what's the alternative for Apple? Require all iPad apps to be changed to also recognize an Apple silicon Mac, too? Whether Apple might eventually change this, with something akin to "Windows Universal"-style apps?

I will assume you meant the most recent macOS version for this Mac Pro, and not the most recent High Sierra version. This Mac tops out at Mojave, with a Metal-capable graphics controller installed.

This API went deprecated at iOS 13, and you'll be rewriting it. Whether to a new API, or also to Swift, etc? What Apple offers: https://developer.apple.com/documentation/network/network_functions Closest analog is nw_parameters_create_secure_tcp, func nw_connection_create, etc. Examples: https://developer.apple.com/documentation/network/implementing_netcat_with_network_framework https://stackoverflow.com/a/59523101 If you prefer a C API outside the purview of Apple, you may want to import libsodium, or libressl / libtls, or OpenSSL, into your project.

This certificate fails on current macOS, as shown from the following certificate dialog from Big Sur macOS 11.4: Your certificates are seemingly from a batch that was mis-issued by your certificate provider. You will want to ask your certificate provider to re-issue your certificate. You might also want to ask why your certificate provider didn't already notify you about this, too. Here is an article about the issue: https://sslmate.com/blog/post/apples_new_ct_policy

Low-level graphics user interfaces have long involved platform-specific APIs, or higher-level and more portable interfaces. The former tend to be faster, more efficient, and more capable. The latter, well, the latter tend to be higher-level APIs. Some folks will partition their app designs into hunks, with platform-specific code isolated from platform independent code. Graphics APIs tending to be platform-specific. Sometimes different UIs for the same platform, for some apps. For more portable graphics APIs for apps, Vulkan is going to be interesting to you (MoltenVK with Metal, etc), or a language-specific framework. Maybe using Unity or Unreal Engine, depending on your targets and apps. As for Microsoft Windows 11, Apple doesn't usually post their future plans, and—Microsoft announcements and PR and press aside—Windows 11 has yet to be released. And much like Apple and Metal, Microsoft has their own preferred graphics interfaces for the folks writing apps for that platform; DirectX, etc. There's no good answer here, and different apps and different approaches have different trade-offs.

Your reverse DNS translations are probably incorrect, which will derail secure communications.

At the risk of asking what may be the obvious, and given IP routing is dynamic and can change at any time, establishing a VPN (SSL/TLS/HTTPS/DTLS) within the app seems expedient, and avoids trying to finesse the already-volatile network configuration? If the app needs to check whether it has a network path, try the path. That’s easiest. Either directly to the target host, or (if the target is also accessible externally) maybe establish a test SSL/TLS/HTTPS/DTLS communications with a known host; to a host that is only accessible to the app when operating within the target network or when some other tunnel is active into he target network. Polling the connection state for IP routing… gets ugly.

You're seemingly approaching this as an end-point, and not as yet another waypoint of what may well be a half-century of working, and ongoing learning. In IT generally, and with Apple and other major vendors more specifically, you will never be done learning, will never know all you need to know, and will never stop having to learn. Not if you want to keep going in this business. If anything, you'll find you know less about more, as the whole business grows and as computers are entwined into everything. Much of the technology, and various of the hardware and software vendors, what you have worked on and learned for today will be outdated and outmoded and there'll be work to replace it in five or ten years, maybe in twenty years for the largest installations when the whole factory is rebuilt. Punched cards and 16-bit computing aren't that long ago. Where we'll all be and what we'll be using in the next ten or twenty years? The biggest and second computing vendors from the 1980s are niche and gone, now. As for which of the Apple platforms to learn, it doesn't much matter. They're all related. You'll need a Mac for the Xcode tooling and can develop for all of the Apple platforms from there, or you're using an iPad and developing from there with the playgrounds support announced in WWDC 2021. The former costs more, of course. Find the available course materials that interest you and that you can afford, and find a problem or an app or potential employers that are interesting, and have at. The available materials at the depth you need at a price you can afford is probably the biggest deciding factor in your path, at least for now. But don't think this learning stuff ever ends.

Maybe this? https://stackoverflow.com/questions/46828387/***-app-is-damaged-and-can-t-be-opened xattr -rc /Applications/YourAppName.app

Installing beta versions on any system that that needs to remain stable and available is... unwise. Wipe the storage, and perform an install of Big Sur. You might have to use the Apple Configurator 2 app from another Mac to reset the Mac, if this Mac is M1. https://support.apple.com/en-us/HT204904

Try the update while booted in Safe Mode: https://support.apple.com/en-us/HT201262 If there's an add-on VPN client app around, remove it and restart and test the update again.

Revert. Erase your storage, and restore your most recent pre-beta backup. Or wipe the storage, and perform a clean install of Big Sur. Otherwise, you're on the beta until it goes into production. macOS doesn't have downgrades. Don't install betas with hardware or apps or data that needs to remain available. Run betas with copies of production data where production copies are permissible, and with test data, and with test systems.