PinkElephant

Version info tells you need to update.
Case is cold, easy to fix.

Maybe try to switch off (or on if it is off) Hardware Acceleration in the Windows apps settings.

You can check access on your account information.
It is either access attempts that failed, or a stuck notification. If you don’t want to setup 2FA now (which is recommended), you can click to proceed, and break it off on the next page. This usually stops the notifications.

Did you ask Postach-support yet ?

The app from the website and the AppStore ARE identical, as far as EN is concerned.
But MacOS runs AppStore versions in a sandbox, each one in its own. This to avoid that malware injected into one can affect another. This at the same time hinders one app to „talk“ freely to others. And this leads to weird, sometimes hard to produce errors.
On the other hand it allows Admins on managed devices to allow users to install software from the AppStore, blocking all free installs.
If you are master of your Mac, I would avoid the AppStore version if a free version is available.

You need to get an authenticator app, like Google authenticator, Microsoft a. or (my choice) Authy. EN says Google a., but most others will work.
The backup codes are generated when setting up the app. Print them and store them - as long as the app is working, you won’t need them. Don’t put them into your EN account - if you need them, you can’t go there.
https://help.evernote.com/hc/en-us/articles/208314238

Ask support - maybe they can check on their end.

No issue, with a subscription you can connect as many devices as you wish.
Just download the iOS client from the AppStore, open it and log in. It will connect to your account and draw an initial load from the server.
You can choose per note or notebook to have a full download for offline use.
The iOS client is pretty similar to the Android client, but less bugs and more stable. Notes will sync across all devices using the EN server.

Each note is a folder. In it are 2 files, or more. The database holds metadata only.
Save the whole folder.
Personally I have it copied by TimeMachine. In addition I have installed the GitHub project that saves the entire content via a Python script. In an additional script it can convert the database into one ENEX file per notebook, automatically.

Works for me, Mac client 10.60.4.
Maybe your local database is corrupted. In this case log out, quit the app, make a full uninstall using Revo Uninstaller and restart the PC. Install EN again from the EN website, open and log in. When its open you need to leave it run in the background, to give it time to download all content.

And what exactly is the glitch ?
The light color tags below the blue ones ?
This is no bug, its a feature. EN offers some additional filters based on whatever algorithm to allow you to quickly narrow down the search / filter result further. You can add them with a single tap.
If you mean this, it would be a regression if it would suddenly not show any more.

We are not support. We are paying users - more precisely we are the people who’s payments enable EN to give others a free ride.
We are not staff either. We are forum members, and we can call white white, and black black, within forum rules of conduct. You got sound advise to reach support (not reaching it was again connected to a mistake you made on the support page).
Personally I run 2 Free accounts myself, for testing purposes. I need to unsync from time to time as well, and I never had myself stuck with no options left. So my personal experience tells me you took several bad turns to get where you are. I could be wrong, but that’s sometimes the case with experience driven reasoning.
However, you are now in contact with support. Wish you luck in solving your problem.
BTW your only problem in fact is that you stepped over the limits of the Plan you have chosen for yourself - and now want to avoid to solve the issue by simply making a one month payment. All your hazzle with support will cost more than this single payment - again burning money we paid EN to do reasonable things, not talking chichi and minimi with tight handed Free users. But that’s my own problem, isn’t it ?

Subscribe …
Ah, no, bad move: Top right „Probephase auslassen“ will take you to your Free account.

Search the forum, there are plenty of threads about this topic.
The easiest way out is to update your client to 10.60. Your client should show that this update is available. If not, you can try to download it from the EN website, and install manually.

Looking at the wrong places, maybe ?
https://help.evernote.com/hc/en-us/requests/new Access to support is a subscribers feature.

Yes, that’s confirmed.
You can use any authenticator app instead, not just Google Authenticator.
Personally I use Authy, which works on most platforms and is independent.

There is a number of posts about it already.
The trick seems to be not to set filters. Search first, then reduce the list by filtering.

Probably some data got stuck, and the app tries to resolve this by syncing again and again.
This can usually be healed by this:
Log out. Use Revo Uninstaller to install all parts of EN from the PC (you get Revo from the internet, it‘s free). Then restart the PC. Reinstall EN from the EN website. Open it, log in. Now you have a fresh install, without residue. You can use it right away, it just may be a little slow with attachments, because it needs to download them.
Leave the app open in the background while it is downloading your notes to the local copy.

If it looks like that for longer than a few seconds, probably a corrupted local database. EN is then crunching on it, and because it can’t finish it enters a loop.
Log out, make a full uninstall, including the local database. I use the app AppCleaner - the MacOS uninstall will NOT solve such an issue, because it keeps the local data.
Restart the Mac, reinstall using the direct download from the EN website.

If you searched the forum before posting, you would have found a number of existing threads describing this bug for 10.59.5, both for Windows and Mac.
Currently the only fix is to roll back to 10.58.8, and prevent the client from auto-updating again by modifying 2 .json-files. No recommended, unless you feel at home in your PCs engine room.
There are reports about a next release 10.60 for next week - but as users we can‘t tell if it will address this bug.

The yellow highlighter is not from the in-Note-search. The yellow highlighter is from the search for the note, and it remains active as long as the global search field is holding the search term. Both searches are independent, and it is not a bug that once the in-Note-search has terminated, it will fall back to the still active note search.
To get rid of the yellow highlighter, you need to terminate the general search as well.

Features are not important, in general. Only those features are important that you actually use. And then it’s often the nasty little details that will bite you.
So identify your use cases, identify apps that support exactly these, and then simply run a trial, with a few notes.
It must fit your use cases, not general ones.

Just tried the stack:mystack search:
Search for a word that exists in several stacks, without a stack argument: 178 hits Search with the stack specified: 64 hits Search with the stack excluded: 114 hits Note that the 2 later searches exactly add up to the first one. When probing the results, the stack argument has properly been used to restrict the search results.
If it now works for you as well: Fine. If it doesn’t, something is different.

For screenshots I actually use the build in screenshot tool of iOS. I have configured my iPhone to take a screenshot whenever I make a double tap on its back.
I can then add markers and text, and share it directly into EN, without using the camera roll.
On the Mac I use the menu bar app Shottr, with even better capabilities.

You need a working device, and go to your account page there. On the devices tab you see which clients are registered.

Not sure about it, but I think direct install and AppStore install already counts as 2 devices.
So does the web client, even when used on the same physical machine.
You only have 2 unsyncs per 30 days either.
So it may be with all the movement between clients, your possibilities to solve this on Free are already exhausted.
But as said above, first check your devices.