I'm not a fan of it (poorly documented, not very sensible setup if you ask me and it defaults to ZeroSSL [and is bought by it], a different, commercial [but free using the ACME protocol] CA, although it can be configured to use Let's Encrypt), but the client called "acme.sh" has a lot of DNS implementations.
I don't know what the capabilities of "opnsense" are, but "acme.sh" is an ACME client written entirely in Bash with just a few dependencies (I think OpenSSL, stuff like that) and has a ton of DNS API scripts available. You can check the latter out here: https://github.com/acmesh-official/acme.sh/tree/master/dnsapi You might also find other dynamic DNS providers among the list. Don't ask me which one is better tho
ive got this on my opnsense FW, its a package/plugin that you install
just trying to figure out aswell as having a DDNS provider (which i do noip) whether i can have one provider that does both acme client and ddns or whether i can just have the acme client and that also does the DDNS for me
It actually indeed doesn't make much sense to me. It seems you're thinking a DDNS provider can also do some "ACME" stuff or the other way around and have an ACME client do some "DDNS" stuff. While in reality, it's not one thing doing both but always two things doing two separate things.
It seems the PR you're quoting added acme.sh to opnsense, so it might be that any DDNS provider supported by acme.sh is also supported by opnsense.