I have a couple of enthusiast friends who use CompactFlash-to-IDE adapters, and that’s one of the upgrades that almost makes it worth it. You still get the full retro experience (well except for the actuator arm seeking sounds), but on the plus side you don’t have to worry about failing magnetic hard drives.
Also this looks pretty neat as well
Well, this computer is too old for IDE (but see below). :) Looks like it's something called MFM, driven by an entire expansion card that hooks up to the hard drive. But I get what you mean. My oldest tower is running Windows 2000 (since it has a serial port on the motherboard, it comes in handy... for transferring files to/from the IBM PC.) and that has IDE so I could use that for MS-DOS as well (and would be able to run 90s DOS games etc), I'm sure, but with a ~20 year jump in technology (or about half way between the original IBM PC and today).
Interestingly, https://www.lo-tech.co.uk/wiki/Lo-tech_8-bit_IDE_Adapter_rev... or better yet https://www.lo-tech.co.uk/wiki/Lo-tech_ISA_CompactFlash_Adap... looks like it would work if needed, and then using a CF to IDE adapter like you mentioned.
My first PC had an ST-225, and I'd like to confirm that it is indeed MFM. (I miss the gronky startup sounds from that thing.)
If you want to modernize the storage for that old PC, then Lo-tech is probably a good choice. They've got a wonderful all-in-one card that includes a mounting bracket, fits into an 8-bit ISA slot, and accepts a CF card directly: https://texelec.com/product/lo-tech-xt-cf-lite-rev-2/
File transfer can be done a number of different ways, including serial ports (USB to RS-232 adapters generally work fine), floppies (USB 3.5" floppy drives are awesome and cheap), and: Networking.
Around the turn of the century, I briefly had an already-old XT machine that had no hard drive, but it did have 10BASE2 Ethernet and Hercules-compatible graphics built into the motherboard.
It was a fun little adventure to get it online with my then-modern LAN and I did a number of unlikely things with it (including a graphical web browser), but the most practical thing it did was connect to a Samba share on my Linux box. It worked great. Old 8-bit network cards are not particularly expensive.
It all depends on how far down the rabbit hole you want to go. :)