Linux Ubuntu - Internet Routed Traffic Websites Loading Issue

So, I’ve got a weird networking loading issue occurring on Linux Ubuntu (24.04 LTS).

My Setup is:
Internet modem > Macbook with WiFi (running macOS Monterey) > Ethernet cable > router > Ethernet cable > desktop PC (running Ubuntu 24.04 LTS)

I can load some websites, but not all of them. I don’t understand why, or what’s causing this.

I can easily load Google websites like Gmail, YouTube, Google Images, etcetera…
I can even load the main website, Level1tech forums,
other sites like Patreon, Wikipedia, CrunchyRoll, Kick

But there are other websites that I can not load, like Twitter, ebay, Craigslist, Twitch, Newegg, Amazon, 4Chan, Reddit, imgur, etcetera…

I doubt these major websites would be down, and none the less for this long, so I’m pretty sure it’s an issue on my end.

Can anyone help?

Edit- I do not have this issue when sharing, and routing an Internet connection running through Windows, the setup being:
Internet modem > Macbook with WiFi (running Windows 10) > Ethernet cable > router > Ethernet cable > desktop PC (running Ubuntu 24.04 LTS)

Does it work when you connect to the modem directly?

Why are you going through a Mac?

Mac probably filters out websites that don’t include some Apple subscription /s

It looks like an mismatch mtu problem, macos is probably fragmenting the packets cause they are too large to handle whole.
So the main fix is reducing the MTU on your Ubuntu cause that’s what’s most likely sending the very large packets back through your MacBook and the reason windows doesn’t have that issues because all of them handle mtu differently

Because the same sites load when the Mac shares the connection from Windows, it’s likely that full-size packets are being dropped on the macOS Internet Sharing path. I’d test that from the Ubuntu desktop with ping -M do -s 1472 1.1.1.1, then lower the size by 20 at a time until replies come back.

If a smaller size works, add 28 to it and set that as the MTU with nmcli connection modify “Wired connection 1” 802-3-ethernet.mtu 1400 (use your number and the name from nmcli connection show), then run nmcli connection up “Wired connection 1” and reload Amazon.

Drafted with AI, reviewed by me.

Reporting this same issue is happening on the desktop running Windows.
Edit - Windows 7

Setup being:
Internet modem > Laptop/Macbook with WiFi (running macOS) > Ethernet cable > router > Ethernet cable > desktop PC (running Windows)

Edit- This issue is not/did NOT happen on/running Windows 10
Setup being:
Internet modem > laptop/Macbook with WiFi (running macOS) > Ethernet cable > router > Ethernet cable > desktop PC (running Windows 10)

Edit2- Windows 7 issue was fixed with a reboot, will test/see if there is a difference on/with Linux/Ubuntu
Edit3- Should be noted that Windows 7 recognized it as a new network/profile

Alright, I don’t know what the fuck is going on right now.

I rebooted, and it’s working like nothing happened.

I’m assuming a clock/system clock/time/security certificate “hand shake” issue by/per operating system, being out of sync/out of date. If so, that’s just one of the issues if/when you run multipe operating systems, and each one relying on/using a different one/setup/method.

Edit- it is NOT clock/time issue system related. Just rebooted back into Windows 7 to test, the clock is off by hours, and the issue does not occur.

Managed to get the issue to reoccur. Specifically using macOS, and macOS (both systems).

Setup being:
Internet modem > laptop/Macbook with WiFi (running macOS) > Ethernet cable > router > Ethernet cable > desktop PC (running macOS)

Even with rebooting both systems, the issue still occurs/does NOT leave/cease/stop, etcetera…

Edit- shutting down the desktop PC, and turning it back on again, does NOT work/solve the issue, etc…
Edit2- Noticed an issue loading between browsers on Ubuntu, Firefox will not load, Google Chrome will.
Not sure what the reason for this is.
Edit3- Okay, really weird, managed to get the OPPOSITE to occur. After unchecking Internet Sharing in macOS, physically disconnecting the Ethernet cable, rebooting, rechecking Internet Sharing, and plugging in the Ethernet cable, Firefox will load, but Chrome is/does not.
Edit4- After a reboot on the desktop PC, Chrome loads now too.
Edit5- This is really annoying. I’ve gotten to a point where the web browsers themselves will, or won’t be able to load certain sites, but the others/opposite (Chrome, or Firefox) will.
Edit6- Switching operating systems alone did NOT work.
Edit7- Disabling WiFi on the desktop PC (running Windows 7), and rebooting, made the issue occur in/under/for Windows 7.
Edit8- re-enabling WiFi on the desktop (running Windows 7), and disconnecting from the network, so that it only runs off the Ethernet network connection, did NOT solve the problem.
Edit10- Physically disconnecting the Ethernet cable from the desktop PC to the router, and then re-connecting it, did NOT work.
Edit11- Physically disconnecting the Ethernet cable from the desktop PC to the router, rebooting, and then plugging back in the Ethernet cable did NOT work, if anything, made things worse. Now, I can’t load web pages at all, and now it’s/Windows is saying there isn’t even Internet at all.
Great…

Got it working again, …atleast for Windows… 7…
Physically disconnected the Ethernet cable from the desktop PC to the router, and plugged it back it.
So, it must have been turning off Internet Sharing, and turning it back on, in combination with some order of this.
None of the systems rebooted when this happened. Everything was up, and running. Really weird.
Edit- Nevermind, some websites/web pages do NOT load.
Edit2- Got Windows 7 working again, required a reboot. Without the reboot, only certain web pages would load. Works/working across all major web browsers that I use, Firefox, Chrome, I don’t use Edge, but it works there too.
Edit3- Even disabling the WiFi on the desktop PC, and rebooting, works/worked.

I am NOT having this issue for Windows 10. Everything works. Every website, every webpage, everything. Chrome and Firefox.
Edit- Okay, so not all websites load in Microsoft Edge, but seriously, who even uses that shit anyway.

Last edit (Cancelled, issue still occurs on Ubuntu)- Okay, so, based on/upon my previous experience dealing with Mac’s, and even referencing to Linus, from Linus Tech Tips himself, the idea of a very long loading time comes to mind, and that is what I assume. Linus had to wait a long time for something as basic as files to show up in Finder. I am assuming that this is the same case, atleast for Networking/Sharing on macOS.
-Got it working on macOS, Firefox, and Chrome, all websites/web pages, no issues.

Current status for Linux Ubuntu is that it only loads specific/certain/some web pages.
Edit-UPDATE WOW. Rebooting into Windows 10, and then back into Ubuntu makes Ubuntu work.
What.
The.
Fuck?
Can someone explain what’s going on, or why this is?

Reconfirming, everything works on the desktop PC, macOS, Windows 7, Windows 10, and Linux Ubuntu, web pages, browsers, everything.
Edit- even unplugging the router, and plugging it back in, simulating a power loss on it, and the router coming back on, everything works fine, like nothing happened/there’s no issue at all. Really stumped on this one.