Got this via Mastodon which will not let me search for the source.
If you're in the US, when you set up Windows for the first time, select English (Europe) or English (World), not English (US). That will stop it installing all the bloatware that USians are not protected from but everyone else is.
It's definitely a US thing, I'm on English (Singapore) and have not seen an ad, ever. I was perplexed by all the complaints of ads in the start menu and wherever, until someone pointed to me that it was a US thing.
You must switch back to English (US) after installation if you want access to Microsoft Store (and even if you don't, you probably should because most apps are now there).
I've seen a few tools to suppress most telemetry such as ChrisTitusTech's winutil or O&O ShutUp, maybe you could give that a try. Microsoft is really pushing hard Bing & Edge...
Also, as a Linux user, I must obliged to the rules and say there's alternatives out there if you want to try something new. :-) !linux@lemmy.ml
Ah okay, I didn't know people used it that way and I don't do XBox game pass or anything like that. It makes sense. My only real experience with windows store apps has been my work computer trying to install a "personal use" version of Microsoft teams from there and apparently I had to get the professional version through M365 downloads.
From what I've seen online, it must be done during installation. So short answer, no.
As others have said, you could also backup your data and do a fresh installation (from a boot media, not from Windows itself just to be extra safe).
ThioJoe also has a video talking about this English (Europe/World) thing and also provide a Powershell script to delete Windows bloatware. This option could be interesting if you don't want to reset your whole installation.
Throw all your important stuff onto a drive thay doesn't contain the OS. Then remove the drive and wipe the computer. You can set it up again and choose the non-bloatware options.