I can't stop but wondering what kind of coins and tokens those are. The majority of shitcoins are Ethereum-based, so he can just keep those on his Ethereum address on his Ledger. Maybe he doesn't know that and I wouldn't be surprised if he didn't.
I avoid all shitcoins, so I'm totally out of the loop on this, but aren't there a bunch of other trash centralized coins which allow to you launch your own even trashier centralized tokens on top of them, such as Tron and BSC? Can you store those on a hardware wallet? Might be better to just stick to coins which are hardware wallet compatible if you can't figure out a better way to store the other ones other than to save a seed phrase on your computer. (Although if you can generate addresses for a coin via a seed phrase, then there is no reason that it couldn't be stored on a hardware wallet, except that the developers don't care enough to build wallet software which can do that (which is even more of a reason to dump said shitcoin)).
For everything else, you have to rely on installing/uninstalling to work with an app you need at that moment in time.
I've never understood why people make such a big deal of this. It takes literally 10 seconds to swap apps. Perhaps if everybody wasn't in such a rush they would take the time to double check addresses properly as well.
Besides not using Google, I find not using Windows equally difficult. I agree with all the privacy advantages and similar you may gain by using a Linux OS instead, but that isn't enough to make me a Linux user. I'm a windows user since I was a child. I've used in their terminology and as much as I've tried replacing it with Linux, I've failed.
There are legitimate reasons to use Windows over Linux. I don't think "Linux is hard" is one of them. If you can use Windows, you can use Linux. I would suggest Linux Mint as a first stepping stone if you are a life long Windows user. You will struggle to stumble across an issue which doesn't have a step by step guide to resolve it written by someone in the community.
But yes, much like your bitcoin wallet, your OS is only going to be as safe as the person using it. If you go around saving seed phrases on the same computer you use to browse questionable sites, click on random links, and download random software with no due diligence, then no browser, no OS, no antimalware, etc., is going to protect you.