For what it's worth, I've had quite a bit of success using ACME for devices that don't natively support it by using a sidecar service.
Basically, running the ACME flow on a Linux system and then having it programmatically update the cert/key for the service that needs it. Have done this for my NAS, printer, router, etc.
This is what I do as well. I use acme.sh on one linux server to generate a cert with a few SANs on it, then copy that cert to things like opnsense/truenas/etc either using ssh or their api if there is one.
Downside is that you have to provide root/admin access to copy the key material and also to restart the services. A big no-no for me, even in my homelab.
Basically, running the ACME flow on a Linux system and then having it programmatically update the cert/key for the service that needs it. Have done this for my NAS, printer, router, etc.