Do you know if Lyrion on raspberrypi can be managed totally with a (reasonably priced, small) touch screen?
Yes. There's an application called
SqueezePlay which should do what you want -
SqueezePlay - Lyrion Music Server
I believe this would require installing a Linux version on the Pi with full desktop graphics support, which is something I have never done.
The official 7 inch "Touch2" display is $155
Raspberry Pi Touch Display 2 - 7" 720x1280 with Capacitive Touch
A decent case is the SmartiPi $65
SmartiPi Touch Pro 3
But wait ... I know that touchscreens are
flavour-of-the-month (think WiiM Ultra and Eversolo DMP-A6) but the strength of music servers has always been that you can control them from a smartphone or tablet while you move around your music listening area - and I believe you already have an iPad ready for that purpose? The server really requires no form of direct interaction other than a power button!
You seem to be going down the Lyrion path, and that's great, I'm just suggesting that an onboard display is an unnecessary extravagance.
What’s a good external hard drive brand?
I don't know, I don't use them. Are you considering attaching an external drive to your Lyrion-powered Raspberry Pi? As I mentioned earlier, a music library is at high risk of damage once it's treated as being portable. I strongly recommend making your music storage device stationary - in your case attached to the Raspberry Pi. That now makes your Pi a combined music server/player + network storage device - a powerful and useful combination.
There are quite a number of stand-off mounting boards for a rPi5 which provide connectivity for an NVME storage drive, but I don't like these - they restrict airflow above the CPU. I prefer the type which mount
underneath the Pi, such as this one from Pimoroni (US$15)
NVMe Base for Raspberry Pi 5
Put it all in a matching case (US$15)
NVMe Base Case for Raspberry Pi 5
and you have a neat little music server/player, ready to connect to a DAC.
All of this assumes you have some basic skills to be able to SSH into the Raspberry Pi to generate commands and perform certain configurations.
If not ... I see you have a Mac Mini - alternatively that could work well as a Lyrion server. Just throwing the idea out there.