Sadly, even archive.org took some damage recently for their book lending. They get their share of copyright strikes by big business. Even Vimm's Lair got hit a year or so ago and that included lots of games that weren't even available in the US (or outside Japan).
I am not surprised. They host a lot of material that is, like it or not, still protected by copyright laws.
We may not like it, but we don't technically have much of any rights. If you once paid for the game, you might be able to make some sort of claim in the courts. Otherwise, you're out of luck.
Abandonware might be abandoned, but it doesn't mean we can use it. Unless they've put the material in the public domain (or given Archive.org some rights), they still very much own the material. Then, in many cases, it's not always clear who owns the rights - and the rights are often owned by multiple entities.
Hmm... I think we can discuss copyright without it being too political. I think we'll find we're on similar pages with the subject. I'm a content creator and even I think copyright laws need to be reformed.
But, all that software is covered by copyright laws - and trademark laws. (We don't get to use their mark, at least for however long it remains valid. Trademark can end much sooner than copyright and trademark requires defense. Copyright requires none of those things and lasts for like 100 years.
I will say that I've
personally been able to find any title I'm looking for. I'm not into obscure JRPGs, for example. However, the hardware I've purchased has come with many titles like that.
If you want a dirt cheap entry to handheld retro gaming - which includes both the ability to use other operating systems and supports an SD card, look no further than the GB300. It's a lot of fun and I spent less than $6.00 USD on mine because it went on sale. It's never very expensive.
That's another one that is truly disposable. As I've moved on, I'd just hand that one out to someone who had some interest (and was local/in my house and talking about it).
You can also find HDDs full of thousands of ROMs and set up with Botocera. As a Linux user, you're quite familiar with this process - 'cause it is Linux. It's a 'live' distro and you just boot to it to get to the games.