Almost all BSD and Linux distros can boot off the SD card and mount their root on USB attached storage. This is better than doing the permanent fusing stuff, for instance, on Raspberry Pis, and there's absolutely nothing wrong with it at all.
Mine is running from a micro-SD card (+adapter on the old boards) since... I don't know, which year did the Pi 2 came out? It's not the same Pi anymore, but I'm re-using that 8gb card ever since.
Why would where this boots from matter? Linux can mount the rootfs from wherever, regardless of where the bootloader and kernel is stored. You can have /boot on sd card and the rest elsewhere on pretty much any SBC.
I just moved my Home Assistant from SD to SSD and it couldn’t have been easier. Using the USB-Sata adapter I plugged my SSD into my Mac and then used Balena Etcher to dump the HA image directly to the SSD. Plugged it into my Pi and it fired up just like it would’ve if it had imaged to the SD card. I was pleasantly surprised with how easy it was and it’s nice to have HA running off of an SSD now.
You can clone it while running as well [0]. For speed make sure the adapter is USB3.0 and plugs into one of the USB3.0 ports on the pi and also that it supports UASP and enable trim on the drive [1].
Read-only sd card works pretty well though in my experience. You can make it rw for upgrades and remount to ro once done. All the files which need write access (but you don't care about preserving) can be "saved" to tmpfs.
With normal install you can just configure unattended-upgrades (on Debian at least) and mostly forget about security updates, they will just happen (can even set a schedule for reboots for kernel updates IIRC).
But IIRC boot on card + root FS on SATA or USB-SATA works just fine and you only get some writes off occasional kernel update
If it is the sd-card then poor installation.