RSA Certificate. not ECC

since lets encrypt uses ECC signature whereas Synology below 7 version does not support it.
anyone have solution for generate RSA certificate?
It is doesnt matter if we should pay.
thank you

Here’s how I generate the certificates for my Synology, note that is my tailscale domain alias, and scrooge is my NAS:

tailscale cert
openssl x509 -in -out cert.pem
openssl pkcs8 -topk8 -nocrypt -in ./ -out privkey.pem

The NAS has openssl on it, so I can run that directly from an ssh session. You can then use the web front end to load the keys.