As a former sysadmin, this is correct.
If you don't want to get a new device, you can try Android TV on x86 with the official Jellyfin app. I have no idea if it'll work, but it's worth a shot. https://github.com/LineageOS-TV-x86
Hey. I realise my comment may have come off as rude and made me sound like an asshole. It was not my intention to be disrespectful, apologies for that. The reason I posted that is because I read your post (thanks for taking the time to write and share it) and it left me a bit puzzled. I respect wanting something stable, familiar and that requires minimal maintenance, but you seemed to imply this is not possible with a more "traditional" NAS setup. Many of the points you raised about wanting an applliance-like experience are equally achievable on most Linux distros, with no license fees, and with a lot more flexibility, should you need it in the future (although I understand you don't need or want it).
Take Debian for example (a.k.a. the world's most boring distro, in a good sense). With the knowledge you demonstrated about the underlying services involved (BTRFS, Wireguard, etc), it would have taken you no more time to configure the same set of services on a minimal Debian install, it would also run rock-solid for many years, and updates would be entirely at your discretion (as they are with RouterOS). Plus, your pockets would be 50 EUR heavier. But for me, personally, by far the biggest avantage of going with Linux for a data storage solution like this is the possiblity of using ZFS.
Also, have this Debian meme:

"I do not want to play sysadmin in my spare time."
* proceeds to do a bunch of sysadminy things, but on a proprietary OS *
Huh...
Aku Aku from Crash Bandicoot going "Ooga Booga" when you get a mask.
I'm at a loss for words here...
- It's a post
- Contains shit
Community name checks out, have a nice day.
Useless, you don't need a tool to tell whether or not you're running Windows.
Pull an "Albanian virus":
"Hi, I am an Albanian assassin but because of poor technology in my country unfortunately I am not able to assassinate you. Please be so kind to assassinate yourself and then forward me the proof. Many thanks for your cooperation! Best regards,Albanian assassin"
Stop stop, he's already de- oh wait.
antsu
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Also, ruins the joke "hi bisexual, I'm dad". It doesn't roll off the tongue as nicely as the "hi gay, I'm dad".